Build A Model Solar System - 2008 [PDF]

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BUILD AMODEL '■/(/

SOLAR SYSTEM

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APRECISION-ENGINEERED ORRERY

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HOW YOUR

COLLECTION BUILDS There are three stages in the construction of your solar system model. Assembly instructions a r e

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Iprovided for each sub-stage.

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tage two is the principal construction

Sphase, which in all the gear wheels and working parts are added to the

model. Unveil the glory of the solar system with all the planets and moons.

S TA G E 3 Your solar system model is

manufactured using quality ; materials and to high specifications. The gears are solid brass, precisionengineered to high tolerance. Non-

Iworking parts are brass plate; the planets come in silver plate, and the moons are solid silver.

Electrically powered, this attractive and completely individual piece Va r i a b l e

will last for ever and could become

speed .

afamily heirloom.

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!!

B

ring your model to life in stage three with the addition of the

variable-speed motor and gearbox.

YOUR SOLAR SYSTEM MODEL Every element of your orrery is the result of meticulous research

and design, fine craftsmanship and precision engineering. DATE-STAMPED BASE PLATE

Every limited-edition solar system model comes with adate

stamp on the base plate. The engraving work allows you to track the progress of the planets through the constellations of the night sky. A“slip ring” also lets you compensate for Earth’s shifting position against the background stars.

E N G R AV E D G E A R

T

he centrepiece of your solar system model is adecorative, engraved gear plate. The hard-working design is packed

with useful features and allows you to set up your orrery to

track the positions of the planets in real time.

DRIVE SHAFT special 55-tooth gear attached to the

A top of the central axis drives the model’s planets and moons around the solar system. The drive shaft runs from the Sun at the top

of the solar system model, down the centre of the column, to the motor in the base unit.

M E R C U R Y

THE PLANETS

p[ashioned from silver-plate, your planets

a r e hand painted to capture the nature and defining characteristics of the real planets. They slot easily on to afixed pin at the top of each support arm. The major moons of each planet are made from solid silver and mounted on acollar that slips over the pin.

V E N U S

E A R T H

M A R S

M o a n

P h o b o s □e i m o s

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MAGE GALLERY urn to the Image Gallery jaw-dropping space photography and photo¬

T for

realistic artworks. Future

liUSIDE iIMFO: The tnside scoop on

issues include spectacular images from the Hubble Space Telescope as well as the biggest and best of the

all those puzzling questions.^ BREAKTHHOUGHS: Theories

that have changed the world.

Earth-based observatories.

HOW IT WORKS: Explanations of the working parts of the orrery.

ISSUE 5Views along the cliffs of Mercury

SCI-FI: Highlights factual scientific connections with popular culture.

HE STORY !F ASTRONOMY

TECHNOLOGY: Focus on the

equipment used to explore the

race the history and of astronomy from its birth in prehistoric monuments to the high-tech science of space probes and satellites

T development

solar system.

HOW TO FIWO IT: Accompanying locator maps, explaining how to find constellations in the sky.

Find out about the life and

SPACE STARS: People who have changed the face of astronomy.

works of the greatest astronomers

from

Copernicus to Hawking.

ISSUE

2Learn

about

how

the

ancients

tracked

the

Sur

MYTHS AND LEGENDS:

Explains the mythical stories behind the constellations. V.SCJrJKii,;.;.

aR

map

new constellation with every issue, including information on all the most fascinating celestial objects found within it and practical tips on how best to observe it. Explore the night skies with specially commissioned star maps, which build into acomplete collection of

A

all 88 constellations.

IbSUE 2Adetailed star map for Cassiopeia

S PA C E S C I E N C E

-CODE i n t h e; S K Y

SUNEXPLAINED asy-to-understand guides to the

Emost vital theories and concepts in astronomy and cosmology. Learn where the Sun gets its energy

I

from and how we

know how far away the stars are. Also, fi n d o u t a b o u t t h e

strangest space

phenomena and unexplained mysteries.

ISSUE 2Does the Sun mysteriously i n fl u e n c e

events

on

Earth?

ISSUE who

3Hans

discovered

Bethe how

-the stars

man shine

SPECIAL SUBSCRIPTION OFFER Take out asubscription to Build AModel Solar System and in addition to delivery-to-your-door service and never missing out on any components, you'll receive

LIMITED-EDITION PRINTS

three tremendous free gifts.

Three poster-sized, glossy prints reveal the wonders of the

universe. They take you on a

MAGAZINE BINDER

journey from the solar system (Jupiter) into the wider galaxy [Eagle Nebula) and beyond

Keep your collectable magazines stored neatly and safe from harm with this monogrammed, hardback binder.

[Milky Way).

Eagle Nebula r-f*

y

TOOLKIT All the specialised tools and ^v equipment you need to build and care for your solar system model. These free gifts pack away into a practical and sfylish holder.

Jupiter

www.build-soiar-system.com ITO ORDER PLEASE CALL^DUR

et online for an in-depth look at the BuUd Solar System collection. Find an

G Model

introduction and endorsement from Sir Patrick

H O T L I N E O N 0 8 7 1 2 7 7 0 11 3

Moore, avideo guide to constructing the model

There arefwo ways to ensure you don*t miss

You can also subscribe and buy missing issues online -simply and securely.

an issue of~^ rife/ A/Model Solar System:

and interactive links to other astronomical sites.

BUILD AMODEL

1th your newsagent.

i. Taxe out aregwanDT

To reserve your co^, si

Ill in the regular orUir card inside the magazlife and hand it to a

your newsagent. 2 . TA K E O U T A S U B S C R I P T I O N M o d e l When you take out asubscription to Bm Solar System every issue will be sent direct to your door for no extra charge and you will receive free subscription gifts while stocks last. SEE THE SUBSCRIPTION CARD INSIDE THE MAGAZINE.

Sf)LAR SUBSCRIBE TODAY! SYSTEM :

AUNIQUE COLLECTION

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( An Eaglemoss Publication -Every week (N) 1

BUILD AMODEL

SOLAR SYSTEM ^

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APRECISION-ENGINEERED ORRERY

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NTRODUCING the ! t

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Uncover the SECRETS

of the PLANETS ->

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■WITH THIS ISSUE: DATE-STAMPED BASE PLATE, CALIBRATION RING AND FEET '

BUILD AMODEL

SOLAR SYSTEM

^TURES 3

AY O U R S O L A R S Y S T E M M O D E L )

^Learn all about the design and construction of your solar system model and its special featu

SOLAR SYSTEM GUIDE Your journey through the solar system starts here, at the very centre, with the Sun.

MISSIONS

16

Find out about the Voyager space probes, the most well-travelled machines in our solar system.

181

20

IMAGE GALLERY Captured by numerous space probes, these images show our neighbouring planets close up.

THE STORY OF ASTRONOMY Sir Patrick Moore discusses what he considers to be

the major astronomical milestones of our time. 24

S TA R M A P ■We focus on Orion -one of the night sky's most recognisable and impressive constellations.

A S PA C E S C I E N C E

2 6

Discover the story behind Kepler's amazing breakthroughs in the laws of planetary motion C O N S U LTA N T E D I T O R : G I L E S S PA R R O W

I M P O RTA N T !The omry is apredsion-^sgineered kit. it niwt be assembled and handled

with can^ to prevent damage to its

parts, and stored or displayi^ safely to ensure nd parts are lost. !Never liquids or solvents to dean the parts.,For best care, use die polishing dqth and dusting bmshes

supplied vi^ the toolkit (free to

subscriptions customers). on a !When asslWTJbting parts, lay flat table artd keep screws an4ell small

Itemsonatihgiysotheycan't-m^away

and get lost: Unpack alt pari ii nmefutly. !The publisher reserves the to

alter parts and their design at any time.

!Parts not to be sold separately. !Hie publisher cannot replace any parts that are damaged or test by the customer without charge. !The publisher cannot be responsible for any damage that may occur as a result of incorrect assembly or mishandling of the orrery. Please ensure y

»ad all the instructions thoroughly

when assembling the parts.

!All tools must be used with care,

following any safety guidelines provided by the manufacturer. !The publisher cannot be responsible for any injuries caused by any tools or materials.

CREDITS ■

■I I

I

E N D O R S E D B Y : S I R PAT R I C K M O O R E C B E F R S E N C O U R A G E D B Y; T H E I N T E R N AT I O N A L A S T R O N O M I C A L U N I O N

MAGAZINE IMAGES: FQtr) Eaglemoss/Simon Anning, (b) NASA/JPL; 2-11 (orrery photographs) Eaglemoss/Simon Anning, (orrery illustrations) Eaglemoss/Julian Ftetdier, (backgrounds) NASA/ HST; 4-5 (t,b) Pikaia Imaging, (cr) Science & Society Picture Library; 12-13(d) NASA/JPLCaltech, (c) NASA/JPL-Caltech/T Pyle, (br) Science Photo Library/Detlev van Ravenswaay; 14-15(d) Science Photo Library/George Bernard,

Photo ^

Library/A Barrington Br< ,(br) Sci Ubrary: 24(cl.tr) NASA/HST (br) Pikaia Imaging; 25(d) NASA/A Dupree(CfA)/R Gilland(STScl), (tr,bl) Pikaia Imaging, (far) NASA; 26-27(bl,tr) Eaglemoss/Paul Montague, (c) Alamy/The Print Collector, (be) Alamy/North Wind Picture ■Archives, (br) Alamy/Visual Arts Library, London

BOOST ^FLET IMAGES: FC Science Photo

JPL/SSI; 19(tl) NASA/NSSDC, (tr) NASA/JPUU

Library/Julian Baum; 2-3(tl) Rex Featurea/Nib Jorgensen, (bi,c,r) Eagetmoss/Siifion Arming^ (background) NASA/4PL-Ca!tech/J Stauffer/SSC; ‘ 4-5 Eaglemoss/Simon Anning, (badkground) NASA/ESA/Hubble 6-7(bl,cr) Ptitaia Imaging, (tc)

Ariz

NASA/Hubble; (be) NASA, (br) LANU (bru) Rex

(tr) NASA/Walt Fernier, (er) NASA, (b) Pikaia I m a g i n g ; 1 6 - 1 7 ( t l , d , c , t r. b r ) N A S A / J P L , ( b l ) Science Phot ,(ter) Library/Science

Science Photo Library/Peter Ryan; 18(tl) NASA/ a, (cl) NASA/JPL, (bl) NASA/JPUSSI, (br)

NASA/GSFC; 20(tl) Rex Features/Nils Jorgensen, [cr) Alamy/ Richard Wainscoat, (be) Bridgeman Art Library/Philip Mould Ltd, London; 21 (t) Robert Gendler (robgendlerastropics.com), (br) Science Photo Library/Sandford Roth; 22(tru) Getty Images/Blank Archives, (bl) NASA/CXC/ CfA/M Markevitch et al/STS /Magellan/

Features, 8(tl) Eaglemoss/Simon Anning, (tr) TA

Rector/BA Wolpa/NRAO/AUI/NSF &N0A0/._._^

AURA/NSF, (c) Pikaia Imaging, (cr) NASA/JPfaffl^| (background) NASA/ESA/Hubble. ■’'R E P R O D U C T I O N :

Stormcreative PublisI

ig Limited

UArizona/D Clowe et al, (br) NASA/JSC; 23(tr)

Courtesy of Patrick Moore, (bl) Science Photo

PRINTING: Century Litho (Truro) Limitei

Eaglemoss Publications Ltd, 5Cromwell Road, London SW7 ^HR WARNING! Accessible gears and small parts.

Keep out of reach of children. Keep this information for reference. Applies to all issues of 'Build AModel Solar System'. ©Eaglemoss Publications (2008). All rights reserved.

AUNIVERSE in

M I N I AT U R E Bring the solar system into your home with this accurate working model

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for accuracy,

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limited-edition :

collector's piece.

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II you need to do to assemble your solar system model is collect

Build AModel Solar System we"ll take you through all the * construction steps and reveal the solar system’s marvels

and mysteries along the way.

IS

MODELLING the

OLAR SYSTEM Labouring over intricate combinations of gears, the instrument makers of the eighteenth century created the world's first replicas of the solar system. Constructing your model will connect you to this illustrious tradition. he tradition of building working models of the solar system stretches back to the early eighteenth century. Based on

P L A N E TA RY

LINE-UP

Your solar system model includes all

the heliocentric model and constructed around aclock-

the most up-to-date

mechanism, Enlightenment instrument makers created the world’s first functioning representations of the solar system and some of the most beautiful and elegant scientific equipment.

members of our

home system

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THE HEAVENLY BOD IE S

Using carefully calculated gear ratios, the movements of a mechanical solar system closely match the motions of the real ,were planets. These models, which are also called o r r e r i e s

essential teaching apparatus for natural philosophy (science)^ :

INSIDE

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INFO

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he distances between planets in the solar system J

T are unimaginably vast and their sizes range from J minuscule rocks to the gigantic gas planets. These huge \ differences are best summed up with comparisons: If Earth was the size of apea, the Sun would be as big as an exercise ball and it would be about half acity block away With this In mind, your solar system model has had these differences evened out -the planets are enlarged, but still correct In their relative sizes, and they have been brought closer to each other and the Sun. This gives you ascaled representation of the solar system that is both practical and desirable.

SUN: 1.4 IMERCURY: 4880km diameter; 58 million km from Sun million km : V

VENUS: 12,100km diameter; 108 million km from Sun

diameter

EARTH: 12,800km diameter; 150 million km from Sun MARS: 6800km diameter;

from Sun

228 million km from Sun

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SATURN:

120,500km diameter; 1427

million km from Sun

m : CERES: 950km diameter (approx.);

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JUPITER: 143,000km diameter; 778 million km

419 million km from Sun

teachers of the time. Watching the planets around an orrery is amuch more satisfying way to understand the relationships of the heavenly

m o v e

bodies to one another than complex series of

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A S T E R O I D

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mathematical formulas describing their movement. Once the mechanical solar system is set in

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motion, the stately procession of planets around the Sun begins, with each revolution marking one year in the life of that world. At aglance, it’s obvious that all the planets orbit the central Sun

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and that they all move in the same plane. Orreries

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can also be used to model night and day and the D W A R F S


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JUPITER ORBIT INSERTION:

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S C R A P M E TA L

Apiece of rusted engine or possibly one of the most

important

archaeological discoveries

of the early twentieth century? (Pictures courtesy of the Antikythera Mechanism Research Project.)

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The dials, positioned on the front and rear of the

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box, gave clear indications that the device would

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have been used for astronomical purposes. The front dial is marked with the Egyptian calendar (12 months, 365 days) and has amoveable inner ring marked with symbols of the Greek zodiac, enabling the user to re-calibrate during leap years.

I AHEAD OF ITS TIME

It is generally accepted that this dial would have had three hands, one to show the date and the

other two showing the positions of the Sun and the Moon. Also visible was amechanism believed

to show the phases of the Moon. The dial displays aparapegma (or almanac) indicating the rising and setting of specific stars; these stars are inscribed elsewhere on the Antikythera Mechanism, suggesting the user would have cross referenced what he

discovered. All this is remarkable, but when you consider that two further dials were located on the

reverse of the mechanism, you begin to get some

understanding of just how technologically

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advanced the Antikythera Mechanism Is.

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Since then scientists have offered numerous

A C C U R AT E M E A S U R I N G

POWER WITHIN

theories about the purpose of the Antikythera

The front and rear of the

The dials on the reverse of the mechanism sit

Mechanism. But it wasn't until the 1970s that

X-rays revealed what was really going on under the surface dials on the box. Highly detailed sets of interlocking gears were clearly visible on the X-ray. Cut by hand from asingle sheet of bronze, the

gears have between 15 and 223 triangular teeth.

mechanism were used to track the heavens. G L O S S A R Y

Metonic: After 19 years, the phases of the Moon appear on the same days in the year in this lunar cycle.

neatly one above the other. The upper dial is made up of aspiral, each turn divided into 47. In total there are 235 divisions on this dial, marking the months of a19-year Metonic cycle. Positioned in the centre of this is asmaller dial showing the later and longer 76-year Callipic cycle. Both the

uch like the calibration ring on your orrery, the outer dial on the Antikythera Mechanism was moveable and had aspecific purpose. Scientists were just able to make out the markings

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on the outer moveable dial -it had

been carefully divided into degrees and showed the months of the year. MAKING

UP

FOR

LOST

TIME

The Ancient Egyptian calendar had no leap years, meaning that every year the calendar fell into error by one quarter of aday. The slip ring NEW Allows you the Freedom to set your orrery to specific dates.

allowed the user to move the months

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OLD Showing the inner

and therefore compensate for the

mechanism along with

loss of time.

the moveable outer dial.

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G L O S S A R Y

S PA C E

Callipic: 76-year cycle. the equi\

S TA R S

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(1922-1983)-*

DEREK DE SOLLA PRICE ,

lent of four

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divisions. This shows the Saros eclipse cycle.

Again there is asmaller dial inside the Saros dial showing a54-year Exeligmos cycle. The mechanism inside the box that powers all of these dials and hands is as impressive as

the outside. The technology present in this amazingly advanced astronomical instrument has been compared to clocks from the fourteenth century. What is clear is that ancient Greek

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astronomers were obviously far more advanced than we realised.

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ANCIENt GEAR

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All the geclf^ have teeth with a60°

angle so they can interconnect.

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'"he Lrb , of the bUr\

Struggling through its violent, tempestuous and troubled early years, our local star eventually settled into acalmer period. Discover our Sun as it comes of age...

W

hen the Sun’s core ignited in ablaze of glory around 5billion years ago,

loses 2000 tonnes of mass. The Sun’s internal S

structure reflects this need to move energy away® from the core and expel it into space. This is not as

the young star we met in issue 2

finally stopped collapsing under its own weight.

simpleasitsounds.InordertoleavetheSun,the^

The outward pressure of radiation from the intense

energy is carried in different forms, and the journey from core to visible surface, through roughly 700,000 km of the solar interior, can take many tens of thousands of years.

nuclear fusion reactions at its core began to fight back. Eventually, adelicate balance between the

forces was reached. Then, as the Sun got to work on converting its huge reserves of hydrogen into

helium, it finally joined the vast majority of stars in

THE HEART OF THE MATTER

the so-called “main sequence”. But just because the Sun has settled down into a routine way of life, doesn’t mean that it is any less

The Sun’s interior has three distinct layers. At the centre is the core -the region where hydrogen is

ferocious. It is still in its adolescence. Each second

Super-compressed, the core is dense and very hot

it generates 200 trillion trillion watts of energy and

with temperatures in excess of 15 million °C.

converted into helium in nuclear fusion reactions j

S O L A R

HOW

IT

WORKS

RAOIATIVE

P R O M I N E N C E

^INSIDE THE SUN

Z O N E CONVECTIVE

/

Z O N E

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SUNSPOTS

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he Sun is divided up into different determined by how energy is transported within them. The core produces fearsomely energetic gamma rays. Once inside the radiative zone, gamma rays travel on arandom zig-zag path, being absorbed and re-absorbed, slowly losing energy over many thousands of years.

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The convective zone features

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large roiling masses of gases, transporting heat to the surface the photosphere. This is where the Sun finally becomes visible to our eyes. Beyond this, the Sun’s diffuse corona stretches

C O R O N A

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for millions of kilometres, blending P H O TO S P H E R E

into the solar wind.

PHOTOSPHERE The visible surface of the S u n i n f a l s e - c o l o u r, shot at three different

wavelengths. Sunspots and solar prominences

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can be seen easily.

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then re-emitted instants later. This keeps the core

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superheated, even as the gamma rays lose energy.

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OUTER LIMITS

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their way out of the Sun’s core and enter alayer

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knownasthe"radiativezone".Thisregionisnot

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ii ASTAR IS APHOENIX

J

DESTINED TO RISE FOR ATIME

FROM ITS OWN ASHES!

■ #■*

hot and dense enough for fusion reactions to occur and, as photons pass (or “radiate”) through it, their energy drops. Slowly they transform into less powerful X-rays and ultraviolet radiation. While the core’s diameter is roughly one fifth of that of the of the way to the surface.

At the top of the radiative zone, the falling density and temperature of the Sun’s material mean that radiation is no longer the most efficient way to carry energy outwards. Huge masses of hydrogen now absorb the energy but do not M

SOLAR PROMINENCE

Massive eruptions of super-hot gas, exposed in

m

m

this X-ray photo.

M

boundaries between layers inside the Sun. By measuring movement

Illions of kilometres

separate us but

astronomers can still

in the Sun’s surface,

learn agreat deal about the Sun by “listening” to it. Our local star Is

constantly shaken by

.5^

“helioseismologists”

I

h a v e c o n fi r m e d t h a t our ideas about the

disturbances that

Sun’s interior are

ripple out from its

largely correct.

core and across its surface. Similar to

O

Carl Sagan

entire Sun, the radiative zone stretches two thirds

r

■4T -

Energy from the fusion reactions is produced in the form of packets of electromagnetic radiation called photons. These are the very same photons that make up visible light, but they have many times more energy. The high energy of the photons gives them amuch shorter wavelength than visible light and they are pumped out of the core as invisible gamma rays, the most energetic form of radiation in the universe. The gamma rays are immediately absorbed by the densely packed solar material and

SHAKING SUN Listen to what

sound waves, they are

the Sun "sounds" like at http://soi.

d e fl e c t e d o f f c o u r s e a t t h e

stanford.edu/results/sounds.html.

X CO

;

-

A

J

W :

->'l%f^

.■■

'. --'V?

■:;« .■ .^>■

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/

re-emit it. This material heats up and rises towards the less dense upper regions of the Sun.

■■

Li?

TW^

Meanwhile, cooler material from above sinks

downwards setting up large circulating convection cells that transport energy out of the Sun. This region is called the “convective zone”. THE VISIBLE SUN

At the top of the convective zone, the gas becomes sparse and cool enough to be transparent to the photons once more. Their lower energy means they burst from the gas in the form of ultraviolet, visible light, and infrared (heat) radiation. This is the “photosphere”, the visible surface SUN CHANGES

of the Sun. To the naked eye, it is adazzling,

ITS SPOTS The

featureless disc, but dense filters can block out

grainy solar s u r f a c e a n d large

!sunspot captured by the Swedish Solar Telescope.

S PA C E

Sun’s upper atmosphere contains many T he elements. The key to identifying these is the

i

spectroscope, invented by German optician Joseph von Fraunhofer in 1814. The device split the Sun’s light into aspectrum, allowing him to identify several hundred tightly defined “absorption lines”.

SUN STAR By the end of his life Fraunhofer had been

made an honorary citizen of Munich.

INSIDE

Most prominent are the sunspots -large dark “holes” in the photosphere, often many times the size of the Earth. In reality, these are regions of the photosphere that are less dense and therefore

S TA R S

yJOSEPH VON FRAUNHOFER (1787-1826)

i

most of the radiation and reveal ahuge variety of features on and above the surface.

cooler -they appear dark only because, with a temperature of about 3800 °C, they are some 2000 °C cooler than their surroundings. They come in pairs, but often congregate in larger groups too. Bright lines of hot, dense material, often associated with sunspots, are called “faculae”.

In 1859, German chemists Gustav Kirchoff and

GAS EXPLOSIONS

Robert Bunsen spotted the similarity between the Sun’s dark “Fraunhofer lines” and the bright e m i s s i o n lines” produced when they burnt certain chemicals.

Along the edge or rim of the Sun rise prominences”, loops of cool, red gas. Dark

They guessed that the same elements were causing the lines in the Sun, and identified them

hydrogen, oxygen and sodium in its atmosphere

a

s

wriggly lines across the face of the Sun, known

as filaments, show where the cooler gas of prominences is silhouetted against the brighter background. At times, the Sun can also belch out

INFO

HOW DO SUNSPOTS FORM? Sun generates the most powerful magnetic T he field in the solar system through its shifting masses of electrically charged particles. However,

as the Sun is made entirely of gases, different parts move at different rates. Over time, this

causes the magnetic field to get tangled and it forces its way up through the surface of the Sun in loops.

p -

Where aloop pushes through the photosphere. it forms asunspot pair -amagnetic north and south pole. Gas flowing along the field lines causes prominences, and occasionally, when the

field “short circuits”, it releases huge amounts of energy as asolar flare or coronal mass ejection

THE SUN'S pristine magnetic 1field runs smooth in loops

from magnetic north to south.

days), carrying the field with it.

H

CO

huge billowing clouds of super-hot gas called solar flares and “coronal mass ejections”. These rush across the solar system at very high speeds, and when they reach Earth they rain particles into our planet’s magnetic field, interfering with satellites and radio signals, and producing spectacular displays of northern and southern lights.

o > TO C O

CO

FLAME THROWING

m

Seen through the right filter, the entire surface of the photosphere dissolves into aseething mass of “granules”, each with adark edge and abright

O

centre. These are the tops of convection cells in

the region below -the bright patches mark fresh, hot material rising up from the interior, while the dark edges show cooler material that has already released its radiation, and is sinking back down. The most detailed views of all show amass of

flame-like "spicules’

■vertical tendrils of material

some 10,000 km Ion

rising out of the photosphere.

SOLAR CYCLE

The paths taken by prominences, the upright appearance of spicules, even the ragged edges

of sunspots, all give the impression that the Sun is “hairy” -they are similar to the paths taken by iron filings around apowerful magnet. This is no coincidence -shifting masses of electrically charged particles inside the Sun produce the most powerful magnetic field in the solar system. During a“solar cycle” of about 11 years, the

o

increase in number (see below). Finally, as the spots converge on the equator, they start to cancel

each other out, dwindling away and taking the Sun’s magnetic field with them. After awhile, the magnetic field regenerates and the cycle repeats again -the Sun’s magnetic poles are now reversed

0

SUN CYCLE

Images taken at 120 day increments showing changes in the Sun's

corona during the waning part of its cycle, lurtesy of the Yohkoh

(Pictui

iion of ISAS, Japan.)

compared to the previous cycle -so the r e a solar cycle actually lasts 22 years, rather than 11.

Variations of the cycle don’t just affect sunspot numbers -they drive awhole range of solar activity, including solar flares and perhaps the Sun’s overall

C O

energy output. N E X T:

D E AT H

THROES

- W H AT

WILL HAPPEN WHEN THE SUN DIES?

magnetic field starts out in arelatively smooth,

ordered state, with just afew sunspots occurring at high latitudes. As the field becomes more and more tangled and complex over the course of several

years, sunspots form closer to the equator and he link between the solar cycle and Earth’s climate is still

T controversial, and has become afocus for people who deny that global warming is entirely man-made. The truth is that we know far too little about the solar cycle to understand whether it might be causing an increase in the Sun’s energy output at this point in history. However there is some evidence that the cycle can affect the climate on Earth. In aperiod called the Maunder minimum, from 1645 to 1715, sunspot numbers were unusually low. This coincided with a"Little Ice Age on Earth, during which the climate cooled noticeably, allowing the celebration of regular “frost fairs” on London’s frozen River Thames THE BIG FREEZE Inhabitants of London

have fun "messing about on the river" at a

2LOOPS ofof the field eventually push outtangled Sun, producing sunspots and other activity.

o

f a i r

T W N

OBSERVATORIES Launched on the evening of 25 October 2006, after alengthy delay, the STEREO twin solar observatories set off on ahistoric journey. ASA'S STEREO (Solar

of this is to help us to develop

Terrestrial Relations

agreater understanding of the

Observatory) mission has broken boundaries in many ways. For the first time it’s now

possible to view solar activity in 3D outside of Earth’s orbit. By

setting the observatories

on

a

movement of energy from the Sun to Earth and to explore the way solar plasma and radiation interact with Earth and other planets in the solar system.

Even before the first 3D image

heliocentric orbit, one ahead of

had been viewed the observatories

Earth and one behind, NASA

were forging ahead, breaking all

\

successfully placed two “eyes” in space. Images taken by each individual observatory are

!l!

solar orbit, albeit at different times.

returned to Earth as data in real¬ time and then combined to create

asingle 3D picture. The purpose

used the gravitational pull of the Moon as aslingshot, firing each observatory into exactly the right

W

Dr. Michael Kaiser, STEREO project scientist

the rules of space flight. Although

One of the main mission objectives

S TA C K E D

NASA had used the gravitational

The twin

pull of aplanet to position

observatories

spacecraft in the past, they had

of STEREO is to study Coronal Mass Ejections (CMEs). These are the most powerful explosions in the solar system, packing the power of abillion-megaton nuclear bomb, Clearly visible from Earth, the effects

are carefully secured inside

the fairings j of the Delta

II rocket Just before launch.

never tried to use gravity to affect the trajectory of more than one spacecraft. STEREO set anew precedent and NASA successfully

can be felt as soon as 20 minutes

FIRST VIEW

The very first 3D image of the Sun released

by NASA on December 4, 2006.

C O

m m

o

ability to establish their own orientation, position and orbit and

adjust these accordingly. Having spacecraft that can carry out these functions alone reduces the cost

could cost as much as $70 billion in lost satellites and services.

of the mission. Aby-product of this “intelligent” design is that the remaining instruments can be controlled from separate locations,

Each observatory carries 16 later as the mass of solar material T

again reducing the cost.

instruments, developed in many

batters Earth's magnetic field like a

O R E T S

different countries. The large

freight train. With speeds between their^s^ofar Uriels number and variety instruments of 700,000 and 10 million km/h and fully deployed, the economic impact of acategory 5hurricane, understanding these

on board created adesign challenge for NASA: ensuring that one

“space storms” is of vital importance. Not all CMEs impact

another was essential. After launch

with Earth and not all of those that I

is about the size of abus.

do have devastating effects; some

The largely autonomous spacecraft are designed with the

instrument did not obstruct

and deployment, each observatory

cause minor disturbances with mobile communications or TV and

The huge

radio signals. However one model estimates that a“super storm”

transmitting data

disc used for back

to

Earth-

In the next few years NASA is planning to return to the Moon

with people and robots. The effect of solar explosions on both astronauts and machinery like the International Space Station could be devastating. But with STEREOs help, any settlement in space or here on Earth should be safe from space weather!

O CD C O

m 7 3




o 73 m C O

The ANGRY SUN As the Sun matures, activity on the surface begins to peak, giving off more light and energy. Technological advances mean it's now e a s i e r t h a n e v e r t o v i e w o u r c l o s e s t s t a r. he Sun, now in the middle of its lifecycle, is getting hotter and hotter. Temperatures are believed to be increasing by about 10 per cent every 10 billion years. Nuclear fusion at the core keeps temperatures at a

searing 15 million °C -the surface by comparison is ablistering 6000 °C. Although it takes along time for the energy to make its journey from core to Surface and eventually into space, when it does the results are truly explosive! 0

■>

[1] SOLAR FLARES

Large explosions of plasma, known as solar flares, blast from the Sun's s u r f a c e . S m a l l e r fl a r e s

loop back due to the

effect of the Sun's gravity.

[2] DARK SPOT Sunspots are caused by loops in

the Sun's magnetic field that lower the intensity of heat escaping from the photosphere. The lower temperatures give them their distinctive

dark appearance.

i

A

[31

CD m

O ■

[3] AURORA BOREALIS The Northern Lights are caused by charged

[4] ASUPER POWER The Atlantis space

particles hitting Earth's upper atmosphere where they react with oxygen and nitrogen atoms releasing magical violet, red and green colours.

International Space Station visible against the impressive backdrop of the Sun, less than an

shuttle and the

>

[5] FIRE FROM THE SUN This image of acoronal mass ejection was captured by the SOHO observatory using a coronagraph. The image

shows the plasma trails

hour after Atlantis had

that cross the vast ocean

undocked from the ISS.

of space to Earth.

L O

»HOVENWEEP

O

CASTLE

Built in Utah, by the Anasazi tribe. these remains are believed to

O

house acalendar room.

culture of the megalith builders, offering tantalising hints of their lost

PRESERVED If

it represent stars, including the

not for apolice operation, the

distinctive Pleiades cluster, while

during years when the extra month was required.

0

thought to show the earliest map of the Moon. Even more fascinating

alarger crescent and disc may represent the Moon in different phases. One theory is that the disc was used to regulate the calendar. Twelve “lunar months” (complete cycles of lunar phases) add up to only 354 days, so in acalendar

is the Nebra Sky Disc, found by

based on lunar months, it is

The Egyptians and Babylonians

C O

archaeological looters in Germany’s

necessary to add an extra month every three years or so in order to keep in step with the solar year. Experts think the Sky Disc shows a pattern that occurred in the skies

were the first to leave written

o

Nebra Sky Disc might have

science. For example, patterns

vanished into a

carved on to stone in aburial

private collection.

chamber at Knowth in Ireland are

Saxony-Anhalt region in 1999. The disc dates to around 1700bc,

and belonged to asophisticated Bronze-Age culture. Small dots on

BIRTH OF ASTRONOMY

o

Within the lifetime of Europe’s megalithic culture, more sophisticated civilisations had

C O

sprung up around the

'?D

H C O m

O

Mediterranean and farther east.

records of their astronomical

beliefs, and paved the way for the rise of “real” astronomy in classical times (see later issues), but parallel

X m

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EGYPTIAN CALENDAR

>

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c n T 7 V

H X )

emonial centre at Nabta

o

nsouthern Egypt the ages of the Pharaohs »and years. It consists of

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Fstone rows and burial

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ipparently for sacred 3ngside astone circle ined to significant points ’s annual cycle.

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"-n

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’’ '

m\n^ Tn '

h-^

■ i fi .

(S) NORMAN LOCKYER [1836-1920)

■

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f

■«r u l t

ntiquaries of the 17th and 18th centuries, as William Stukeley and John Aubrey were the first people to study megalithic sites seriously. They were largely responsible for the mistaken belief that the monuments were built by the Celtic druids who led resistance against the expanding Roman empire.

A such

t - ’ -

.

D I G G I N G D E E P E R I N T O T H E PA S T

V

respected astronomer Norman Lockyer, whose discoveries included the element helium, made the first detailed study of Stonehenge, revealing its astronomical alignments. Lockyer’s work paved the way for others, but It

T-

: ^

^was not until the 1950s that Scottish engineer

^AlexanderThommadeadetailedsurveyof

monuments across Britain and beyond, revealing

■ ■ ■

c

PG^MATH Lockyer is credited

If \ the vast number of astronomical alignments and Wthe sophistication of their construction. Thom Is j

.;?C

"

/

wifh discovering'^elrafn and setting 3 Iwidely regarded as the founder of anew science, up the scientific jckirnai,. Nature.

^known as archaeoastronomy.

to these developments, other

PA I N T I N G O N T H E WA L L

FOREVER

non-literate cultures continued

Monuments that reveal ancient

LOOKING

to practise their own brands

interest in other aspects of the sky

of astronomy.

are few in number, but are all the

TO THE HORIZON

The impassive

including the Crab Supernova, an exploding star that blazed in the sky around 1054ad.

The great civilisations of

more intriguing for their rarity.

stone faces of

Central and South America were

A N C I E N T O B S E RVATO R I E S

The Anasazi culture that built

Easter Island's

also fascinated by avariety of

Traces of solar observatories have

Moai

been found in many cultures around

Hovenweep had another focus around Chaco Canyon

the world. North American Indians

in New Mexico -here,

laid out “medicine wheels” that

alongside evidence for more

often have asolar orientation. More

solar observatories, are paintings

impressive is Hovenweep Castle, an

on the rock walls that are thought

imposing monument built by the

to represent astronomical objects

Are they looking

to the equinox sunset?

Anasazi tribe on the Colorado/Utah border around 1200ad. One of the

G L O S S A R Y

chambers in this defensive fortress

Solstices and equinoxes: Solstic

has windows that are designed to

the turning points of the Sun’s yearly progress north and south. Days get

allow sunlight to enter only at

shorter after the

a r e

immer solstice and

specific times of year -the entire

longer after the w i n t e r □Istice. Midway solstices are the equinoxes -when the

room is thought to be acalendar

Sun is directly over the equator and day id night are of equal length.

of some sort.

At around the same time, the inhabitants of Easter Island in the

Pacific Ocean were erecting the famous and enigmatic stone heads or “Moai”. These too seem to have

an astronomical significance -one cluster stands around the coast of

the island, gazing due west towards the equinox sunset.

i

statues.

events and phenomena -for

example, the Maya city of Uxmal incorporates monuments that track the rising points of Venus, the brightest object in the sky after the Sun and Moon.

f

'

■■

before the Aztecs re-inhabited

it and gave it its present name, meaning "birthplace of the gods”. Its builders laid the buildings out on agrid pattern around two great perpendicular avenues, but while I t

most such cities align to the "ordinal” compass points (north, south, east and west), at Teotihuacan

f

the entire grid is rotated by aprecise ‘>4

H I D D E N C AV E

The Pyramid of the Sun (above), under which the

Ihidden sacred

cave was found.

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1

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15.5 degrees. This means that its western avenue would have pointed

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directly towards the setting point of

7D

LOOKING TO THE STARS

the Pleiades star cluster at the time

Many of the Mesoamerican peoples left written accounts of their beliefs (outlined in later issues), but others have vanished

of its construction. The Pleiades were

O

into the mists of history. The great

enormous "Pyramid of the Sun” with

Mexican city of Teotihuacan was

atunnel that leads in this direction.

built in the middle of the first

It seems that the entire city was

millennium ad, about 1000 years

then built around this sacred cave.

important to many central American

civilisations, and archaeologists

O

have discovered acave beneath the

O o CO

F I R E I N H E AV E N

CO

Important celestial events, such as the

Crab Supernova of 1054, did not escape

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o

1

the attention of the

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Anasazi Indians.

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1*^ ;

■

■

3UARIUS .^i

Tjhis constellation in

the’equatorial region of the

sky depicts ayoung man pouring water from ajar The Sun passes through ft Aquarius from late

M.

4 \

AFebruary to early March. i i

-tit

he water jar carried by Aquarius is represented by aY-shaped group of stars in the northern part of the constellation, almost exactly on the celestial equator. From the jar asprinkling of stars flows southwards towards Piscis Austrinus the southern fish.

HELIX NEBULA Acolourful and

complex shell of gas surrounds a central white dwarf in this composite

of imaged from the Hubble Space Telescope and ground-based observatories (above). Glowing

oxygen gas shows up as blue while hydrogen and nitrogen appear red. M2 This great globular cluster

D O U B L E S TA R

The star at the centre of the water jar asterism Zeta (Q Aquarii, is an attractive binary, easily separated by small telescopes. The component stars orbit each other every 600 years or so and at present are gradually moving apart as seen from Earth. DYING STARS

contains over 100,000 stars and

When stars like the Sun reach the end of their lives

measures about 150 light-years across. Even though it is 38,000

they throw off their outer layers to form aso-called planetary nebula, and two of the finest examples the sky lie in Aquarius. The Helix Nebula, NGC 7293, is the nearest and hence the largest-appearing planetary nebula in our skies. On clear, dark nights it can be seen through binoculars in the constellation’s southern reaches as apale, round patch. Its full glory I S apparent only on images taken through large telescopes, when it appears like acolourful flower. as shown here. On older photographs its shape resembled two overlapping loops of aspiral.

light-years from us it can still be seen through binoculars.

m .

ythologists say that Aquarius represents Ganymede, a shepherd boy from Troy. Zeus, the greatest of the Greek gods, became infatuated by Ganymede’s

M

good looks and swept down in the form ^ of an eagle to carry him up to Mount Olympus, where the Greek gods lived. There, Ganymede became awaiter to the gods. In the sky, he is depicted pouring water from ajar -

or possibly the liquid is nectar, which was the

£5 favourite drink of the gods.

i n

hence the name Helix Nebula.

Another planetary nebula with an interesting shape is NGC 7009, known as the Saturn Nebula because

of its extensions that resemble the rings of Saturn STELLAR SWARMS

M2 in northern Aquarius is arich globular cluster ahazy patch in binoculars o r s m a easily visible telescopes. Another globular, M72, is much smaller a s

a n d f a i n t e r.

How the

SUN SHINES Basking in the sunshine on ahot day, you'd be forgiven for thinking of the Sun as abenign provider of light and heat. The violent reality couldn't be more different...

1proton

1 e l e c t r o n

HYDROGEN The

simplest element makes up 74 per cent of the

very single second for the past 5billion years, the Sun has converted more than 4million tonnes of hydrogen gas into pure energy. Despite this output, there is enough material

reside in the nuclei of atoms. They don’t occur

in the Sun for it to continue at this rate for at least

the Sun, where the crushing weight exerted by

readily and need extremely energetic conditions

the bulk of the Sun’s mass creates temperatures of up to 15 million and pressures 250 billion times the atmospheric pressure on Earth.

of the Sun. Its core is

One bucket full of the material in the Sun’s

like an enormous reactor

core is so dense, you wouldn’t stand achance of lifting it.

hydrogen nuclei. 2protons 2 n e u t r o n s

Under such extreme conditions as these,

as its fuel, converting it to the heavier element

matter cannot exist in normal states (as solid,

helium in nuclear

liquid and gas). Instead it becomes “plasma”.

fusion reactions.

This is astrange state of matter, which occurs

HELIUM The next

simplest element

when an atom’s electrons are stripped from the

makes up 25 per cent of the Sun's mass (the

F U S I O N FA C TO R

central nucleus. Material in the Sun exists in a

remaining mass is made

Fusion reactions are

generate super-hot plasma to recreate the

kind of “hot particle soup”, allowing subatomic

reactions between the

up of trace amounts of heavier elements).

conditions inside the Sun.

subatomic particles that

particles to get closer to each other than they ordinarily would, overcome their mutual repulsion

FUSION POWER Earthbound fusion reactors

S PA C E

S TA R S

HANS BETHE (1906-2005) ans Bethe (pronounced “bay-tuh”) was aGerman theoretical physicist who fled Nazi Germany in 1933. After two years in England, he moved to Cornell University, USA, helping it establish its reputation as a centre for excellence in physics. During World War II, Bethe headed up the Theoretical Division at the top secret Los Alamos

prompted him to wonder about

H

laboratory, working on

t h e fi r s t a t o m i c b o m b s .

Later, he moved on to help develop fusion-powered hydrogen bombs. This work h

2^

be considered as free

(very high temperatures and pressures). These are exactly the conditions found in the core of

another 5billion years. Everything happens right in the very heart

that uses hydrogen gas

Sun's mass. Protons can

the mechanisms at work in the Sun’s core. In 1967 he won the

Nobel Prize for his ground-breaking theories on the mechanics of energy production in stars. Despite his work on weapons of

m

mass destruction, Bethe was an

internationalist and apacifist. Along

%

with Albert Einstein, he lobbied for

both anuclear test treaty and nuclear disarmament.

^

1

i

AT O M I C K I T T E N H a n s B e t h e

was atireless campaigner for the peaceful uses of nuclear power.

Helium builds up like ash in the Sun's core.

KEY

P L AY E R S : PROTON Apositive particle found t h e cleus (centre) of atoms NEUTRON Aneutral particle, which acts as ‘glue’, keeping protons together in the nucleus POSITRON Apositively

NEUTRINO

Asuper-fast particle, hardly weighs athing

> o

G A M M A

m

R AY O e a d l y, high-energy

CO

radiation

charged electron

CO " 0

o m

proton

d e u t e r i u m

(hydrogen

t r i t i u m

(‘heavy hydrogen’)

nucleus)

+

t r i t i u m

o

D E U T E R I U M

K

^

Z : ( ‘ H E AV Y

m

1 X

T R I T I U M

IZlHELIUM^

HYDROGEN)

o D

\

o c n

X m

^TWO At PROTONS low temperatures COLLIDE and speeds,

protons

repel each other because of their mutual

2aprotonanddeuteriumcollide

The “strong nuclear force” -afundamental force of nature, more powerful than the force of

positive charge. But get hydrogen nuclei within electric repulsion -makes nuclei stick together. 10-^s mm of each other and it’s totally different! This requires high temperatures and densities.

3

TWO TRITIUM NUCLEI COLLIDE The conditions in the Sun’s core are

ideal for these reactions. The core is 15

million °C and is so dense that even light takes 100 thousand years to escape!

CO

c

z 0 0

X m

!-0 G L O S S A R Y State

of

matter;

-due to the like charges repelling -and undergo fusion reactions (see box above).

output of 4X10^^ watts. It would take 2billion of

the Earth’s most powerful nuclear power stations working flat out for ayear, to match the energy the

Depending on the energy, asubstance can exist in

three states -solid, liquid

FUSION POWER

and gas. Water can exist

In the proton-proton fusion reaction, four protons come together to make helium. The burst of

as ice (low energy), water (normal state) and steam

.(high energy). Plasma is a Ifourth, super-excited state

energy released from each stage of the reaction is what makes the Sun shine with an average power s ■ l

m

i

INSIDE INFO

WHY DOESNT THE SUN BLOW UP? he world’s most powerful use the destructive ,power of nuclear fusion. In an H-bomb, expanding gases blow the bomb

T weapons

m

simply the result of atiny discrepancy in the mass of the end products of the proton-proton reaction. The key is the fact that helium’s mass isn't quite four times the mass of one proton (it’s 3.97 times to be precise). This missing minuscule amount of mass -equal to just 0.75 per cent of the mass of

one proton -is converted into energy during fusion via Einstein’s famous equation E=mc^. G A M M A - R AY T R E AT M E N T

The Sun’s proton-proton fusion reaction produces gamma rays -alethal form of nuclear radiation and the major culprit of radiation sickness. In fact

!casing apart in arapid and uncontrolled

Ireaction, which generates an explosive

m

Sun produces in one second. The phenomenal power output of the Sun is

EQUILIBRIUM to contain the

the Sun produces enough gamma-ray radiation to sterilise the entire solar system. So how did life

H o w e v e r, t h e S u n d o e s n ’ t b l o w i t s e l f

Furious energy

survive this bombardment?

to pieces because the bulk of its outer layers act as acontainment

of its fusion "

force equivalent to about 25 million tonnes of conventional explosive.

vessel. Gravitational forces, created

by the enormous mass of the Sun, pull material In towards Its centre, keeping the reaction controlled and contained.

The Sun is able

r e a c t i o n s .

The answer lies in the density of the Sun.

Material in the core is so tightly packed that gamma rays collide constantly with particles. It can

take thousands of years for the rays to escape and, by the time they do, they have lost much of their devastating energy.

ISSUE i

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PCOMPLETE STAGE one with this ISSUE;

PLANETARM.^ GRUB SCREWS

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!Witness the mighty fall of the S u n i n i t s fi n a l d e a t h t h r o e s .

I S O

P L A N E Tmercury '

!Follow the amazing story of modern-day planet hunters.

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PLANET MERCURY

!Do sunspots hold the answers to the common cold?

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BUILD AMODEL

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SYSTEM -fAPRECISION-ENGINEERED ORRERY

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Will the

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■COMPLETE STAGE ONE WITH THIS ISSUE: PLANET MERCURY PARTS

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BUILD AMODEL

SOLAR SYSTEM FEATURES YOUR SOLAR SYSTEM 3D

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l

!The orrery is aprecision-engineered kit. It must be assembled and handled

MODEL

Complete stage one in this magazine, and find instructions for using your engraved gear.

0

I M P O R TA N T

SOLAR SYSTEM GUIDE Find out what will happen when the Sun dies and what it means for planet Earth.

MISSIONS

with care to prevent damage to Its parts, and stored or displayed safely to ensure no parts are lost. !Never use liquids or solvents to clean the parts. For best care, use the polishing doth and dusting brushes supplied with the toolkit {free to subscriptions customers). !When assembling parts, lay them on a fiat table and keep screws and ail small items on atray so they can't roll away and get lost. Unpack ail parts carefully. !The publisher reserves the right to alter parts and their design at any time.

■■

11

I

!Parts not to be sold separately. !The publisher cannot replace-any parts that are damaged or lost by the customer without charge. !The publisher cannot be responsible for any damage that may occur as a result of incorrect assembly or mishandling of the orrery. Please ensure you read all the instructions thoroughly when assembling the parts. !Alt tools must be used with care,

following any safety guidelines provided by the manufacturer. !The publisher cannot be responsible for any injuries caused by any tools or materials.

10 ^Scientists are constantly scanning the skies in search of new, habitable planets.

IMAGE GALLERY Startling images of the remains of sunlike stars show the eventual fate of our solar system. 16

20’

THE STORY OF ASTRONOMY Ancient Egyptians mapped out the heavens and used this knowledge for practical purposes.

S TA R M A P Use the star map to locate the star clusters and galaxies in the constellation of Pegasus 11

■■ I I

I

UNEXPLAINED

CREDITS

Does the solar cycle explain global flu pandemics, paranormal sightings and revolutions?

IMAGES: FC Hubble Heritage Team; 3Alamy/Don Vail, (I) Eaglemoss/ Julian Fletcher; 4-5{bl) Science Photo Library/Pekka Parvialnen, (tc) Eaglemoss/Julian Fletcher, (tr) Hubble Heritage Team, (br) Eaglemoss/Simon Anning; 6-7(be) Science Photo LIbrary/Detlev van Ravenswaay, (tr) Pikaia Imaging, (br)

Alamy/Jim Henderson; 18(tl) Corbis/

Science Photo Library/Physics Today

Gemini Observatory/Travis Rector,

Collection/American Institute of

University of Alaska Anchorage;

Physics; 8-9(cl) Hubble Heritage

22(d) Science Photo Library/Eye of

CONSULTANT EDITOR: GILES SPARROW

r

E N D O R S E D B Y : S I R PAT R I C K M O O R E C B E F R S E N C O U R A G E D B Y: T H E I N T E R N AT I O N A L A S T R O N O M I C A L U N I O N

Te a m , ( t r ) E S A / N A S A / G B a c o n , ( c r )

Science Photo Library/Mark Garlick,

Roger Wood, (tr) Bridgeman Art

LIbrary/Karnak Temple, (bl) Science Photo Library/Royal Astronomical Society; 19{tl) Alamy/Neil McAllister, (b) Corbis/Jose Fuste Raga; 20(t)

ING/Daniel Bramwich/Nik Szymanek, (cr) Hubble Heritage Team, (b) Pikaia

Imaging; 21(tl,b) Pikata Imaging, {tr)

Science, (be) AlamyA/isions of America/Joseph Sohm; 23{tl,c) Rex

(b) Pikaia Imaging; 10(tr) NASA/JPL, Features/Sipa Press, (cr) Corbis/ (cr) Courtesy of the Shaw Prize, (br) Hulton Collection, (br) Corbis/ CNES/D Ducros; 11(tc) Ball Aerospace, (tr) NASA/JPL, (be) MEPL; 12-13 Hubble Heritage Team;

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With this issue, you can assemble the first stage of the solar system model. You are '-now also ready to collect and construct the mechanical stages of your orrery.

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ou have now collected enough components to build the first stage of your solar systerh model. You can find the instructions for constructing stage one in issue oYie of Build AModel Solar System. With this stage complete, you have the core framework upon

m

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which to build the rest of the mechanism.

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. The base plate, with its engraving, slip ring and feet, acts as a temporary base; the gear sets that will make up the working parts of the solar systern mechanism fix on, and rotate around, the central column; and the drive shaft, with the Sun*and 55-tooth driving gear will eventually ’ *drive the planets around the model, when connected to the motor unit. Planet Mercury fixes onto the driving gear and is already in place at stage one, as is the first of the planetary gear sets. T

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S 1 A O E O N E T h e fi r s t

stage in the construction of the solar system .model is its framework.

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RNS in Set your orrery to one of the most famous astronomical events in the history of man, and amystery to boot!

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our engraved gear, which arrives with

STAR OF BETHLEHEM

issue seven, is etched with three of the

Aclose encounter between Jupiter and Saturn

most important astronomical events in

happens every couple of decades and is nothing unusual, but “retrograde” motions of the planets saw them come together not just

history. It is also engraved with 360° markings, so that you can set your orrery to any past or future planetary alignment.

once, but three times over the course of six

WHAT IS APLANETARY ALIGNMENT?

months. This would have been apowerful sign to star-gazing wise men -Jupiter

When planets come together in the sky, it is called

is the planet of kings, while Saturn was

aplanetary conjunction. This is now regarded as acoincidental arrangement, caused by our Earthbased perspective across the planets of the solar system, as they travel at different speeds on their

seen as protector of the Jews and Pisces

various orbits of the Sun. Ancient astronomers

Saturn. The addition of Mars, the Warrior

thought differently, however. In 7bc, arare and

King, could have indicated to the Magi that the new king would be amighty one -the Messiah predicted in Hebrew scripture.

extraordinary planetary conjunction occurred in the constellation Pisces.

G L O S S A R Y

Retrograde motion: Apparent movennents of the planets in the sky, caused by the Earth’s own motion, when they appear to backtrack on

themselves.

^5^

■ ■■

itself was associated with Israel. This

conjunction was followed in February 6bc

by atriple conjunction of Mars, Jupiter and

E A RT H

JUPITER ^ - S A T

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S^HOW TO SET UP YOUR ORRERY N E P T U N E

360“ ROSETTE

allows you to set up your orrery to any historical

planetary conjucntion

n :

he inner ring of the engraved gear holds the information you need to set up the planets as they would have appeared in 7bc. Each symbol in the ring refers to the position of that planet in the sky. All you need to do is move the planet arms so that they line up with the corresponding planet symbol. Use the symbol key provided in issue one to match each planet to its symbol.

T all

HISTORICAL TIMEPIECE

Yo u r s o l a r

system showing the alignments of the planets in 7bc, from the perspective of planet Earth.

A C C U R AT E A L I G N M E N T S

To move the planet arms, loosen the grub screws locking the planet arm collars using an alien key. These screws are found on the opposite side of the collar to the planet arm. Then looking from above, spin the arms into the correct alignment (shown right). The conjunction is immediately clear to see. You will notice that there are no positions marked for Ceres and Eris. This is because detailed data from their motions is not

SIGNS IN THE SKY Early astronomers read deep meanings into strange

alliances of planets In the night sky.

available prior to 1600. When you set your solar system model to re-enact the Star of Bethlehem, you are replicating an event that was seen as deeply significant by the astronomers of 2000 years ago.

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Tie DEATh of the

SUN

Billions of years from now, our local star will begin to run out of fuel, triggering aseries of events that will eventually e a v e

it acooling ghost of its former self, orbited only by burnt-up lumps of molten slag.

element, into helium, the next lightest element,

regions around the core start to fall inwards. They soon become compressed and hot enough to support hydrogen fusion themselves in a“shell” around the core. The doubling up of energy from

in its core. Each individual fusion reaction turns

the dwindling core reactions and this new shell

or the past 5billion years, the Sun has shone by nuclear fusion reactions that

turn hydrogen, the lightest and simplest

alittle of the Sun smass directly into energy via Einstein’s famous equation E=md. As aresult, the Sun loses 4million tonnes asecond -though

D E AT H T H R O E S T h e S u n ' s fi n a l a c t w i l l b e t o

throw off its outer layers

as aplanetary nebula. Here, billions of years in the future, it is shown

of hydrogen burning means that the Sun’s overall energy output will rise enormously. It will become much brighter, but at the same time the additional

stripping the atmosphere from Neptune.

this is agrain of sand considering that the core itself occupies aquarter of the Sun’s diameter and has atotal mass of some 800 trillion trillion tonnes. f :

felTHEBRIGHTSUNWASEXTINGUISH’D,

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AND THE STARS DID WANDER DARKLING IN THE ETERNAL SPACE.

91

Lord Byron

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But athousand million grains asandstorm make, and eventually the core’s supply of hydrogen will dwindle. The effects may be felt on Earth long before the hydrogen runs out completely (see box on page 9), but when it does, around 5billion

years from now, the Sun will be forced into the next stage of its evolution.

#

■ I

RED GIANT

Throughout the Sun’s hydrogen-burning life, it has kept up adelicate balancing act between ! the inward pull of its enormous gravity and the outward pressure of escaping radiation. The two forces cancel each other out (see The Birth of the * Sun, Issue 2), but as our star’s main fuel supply runs out this delicate equilibrium is endangered and the results are not what you might expect. As the force of radiation from the core weakens, the 6

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his illustration shows the structure

of astar like the Sun passing through the second of its two red-giant phases. An expanding shell of helium fusion is following aspherical shell of hydrogen fusion out through the star. Meanwhile, the spent core slowly collapses, shrinking from aquarter of the Sun’s diameter down, eventually,

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to about the size of the Earth.

As the core grows steadily denser, the layers above it are compressed by its gravity and burn faster and brighter

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as aresult. The star becomes more

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luminous and the pressure from its radiation causes the upper layers to billow outward, cooling as they do so.

HELIUM¬ B U R N I N G SHELL

This means that convection cells, found

only in the upper layers of hotter, sunlike stars, extend through almost the whole outer envelope of ared giant.

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EXTENDED AT M O S P H E R E CARBON-RICH

CORE

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force of radiation coursing through its upper layers

Main sequencer The best, and longest, years of astar’s life. During this stage, stars burn their primary

will cause them to balloon outwards. The Sun

source of fuel -

becomes so much greater, the actual amount of radiation escaping through each square metre of

hydrogen -converting i t t o h fi l i i i m i n t h o c o m

will expand to perhaps 100 times its current size, engulfing the orbits of Mercury, Venus and maybe even Earth itself. And because its surface area

heat towards longer, lower-energy wavelengths, the Sun will have joined the group of stars known as red giants.

The giant phase will be comparatively short¬ lived, lasting perhaps afew tens of millions of years -already processes deep inside the core

around 5500 °C, but in its swollen future, it could

will be moving towards another important change. As the remaining hydrogen reactions die away. conditions grow increasingly hot and dense. They will eventually become extreme enough to begin

drop as low as 3000 °C. As it cools from yellow

fusion of helium into heavier elements. All of a

it will be much less, so the surface will cool down.

Currently, the Sun’s surface temperature is

5/jV^ SPACE STARS

!SUBRAHMANYAN CHANDRASEKHAR (1910-1995) ndian-born Subrahmanyan Chandrasekhar was amongst the first to work out the physics of stellar remnants -debris such, as white dwarfs, left over after astar is officially dead. After studying at Cambridge U Iniversity, he moved to Chica g o :University in 1937, and became aUS citizen in 1953. Chandrasekhar figured out that above acertain “weight” j ■

j

limit (around 1.44 times the mass of the Sun) the white

dwarf collapses to form an incredibly dense, city-sized neutron star or even ablack hole. The energy released in the collapse of the dying star is released FOLLOWING ON a s asupernova explosion -the universe’s Chandrasekhar took most powerful explosions. This upper mass up the reins from limit is named the Chandrasekhar limit in h o n o u r o f i t s d i s c o v e r e r.

R.H. Fowler, his old college professor.

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sudden, the first helium reaction begins. The waste product of the Sun’s life so far becomes its new fuel supply, and the core re-ignites, in an event called the helium flash. Again, the addition of a new energy source has unexpected effects -the rejuvenation of the core chokes off the hydrogen fusion in the shell above it, the star’s overa

energy

FUR-LINED HOOD

The Eskimo Nebula, NGC 2392, looks like a

face in afur parka. With acooling white dwarf at its heart, these patterns are formed by shells thrown off the dying star.

output falls, and it temporarily shrinks and grows hotter again, ceasing temporarily to be ared giant.

As the hydrogen and helium shells push out through the Sun and the core’s contribution dies away to nothing, our star will enter its endgame. The outward force of radiation will overwhelm the

pull of gravity, and the Sun’s distended outer atmosphere will blow away into space. Soon the fusion shells too will tear themselves apart, until

the star’s upper layers are scattered into aseries of spectacular and beautiful celestial smoke rings -

aso-called planetary nebula. RING OF FIRE

But the respite offered by helium fusion will be abrief one. The high

WHITE DWARF

The nebula will continue to spread across space for millions of years, fading as it slowly cools. But it will be kept warmer and brighter than we

temperatures in the core will force the Sun to squander its new fuel supply at aprodigious rate,

burning through it in tens of millions of years, leaving

might expect by fierce radiation from the object at its heart.

behind heavier elements

Stripped of its outer layers, the Sun’s brilliant core lies exposed

such as carbon, nitrogen and oxygen. Astar the size of the

for the first time.

Sun does not have the power

With no outward radiation

to burn these elements as fuel.

pressure to support them, the atoms of the core, by now mostly carbon, oxygen and other heavier

As the core nears the end

of its helium supply, history

will repeat itself. The hydrogen¬ burning shell above the core is re-invigorated and soon ashell of

elements (collectively known as

“metals” to astronomers) will gradually compress under their own weight, until they form adense ball about the size of the Earth. Even though the core is no longer generating energy, it will still be intensely hot, radiating away its remaining energy as brilliant

helium fusion moving outwards in its

wake joins it. The Sun will once again swell to ared giant, but this time, there is no going back, INSIDE

INFO

HOW AN AVERAGE. MIDDLE-AGED STAR DIES .

P R E S E N T D AY O u r S u n i s a n

1 average-weight

FUTURE: 5BILLION YEARS The

2 Sun

hydrogen in its core, but fuel

is now ared giant, burning hydrogen in shells around adead

supplies are running out...

helium core. Mercury engulfed. ’

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star burning

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2FUTURE: 6BILLION YEARS After abillion years, helium burning starts up in the core. The Sun reverts to asmaller, yellow star.

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light. It will have become awhite dwarf

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star -astar so dense that asingle teaspoon w

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of its material weighs several tonnes. Over billions more years, the white-dwarf Sun will gradually dissipate its energy through its radiation. As it cools, the light it emits will gradually dwindle into lower energies and longer wavelengths, until eventually the star produces no more visible light. At this point, the Sun will have reached its ultimate stage of evolution -

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ablack dwarf. Our star slife will end not with

■

e’ve got about another 5billion years before the Sun swells into ared giant, but the Earth could be uninhabitable long before that. Over its history, the Sun has grown hotter and brighter, and will continue to do so as it ages. Short-term climate changes aside, we probably have about abillion years before Earth gets so hot that the oceans evaporate -and 3.5

w

billion years before gone completely. As enters its red giant atmosphere will be

they are the Sun phase, the “boiled off”.

abang, but with along, slow whimper.

BARREN WASTES Dry and airless, eventually only heavy

N E X T: T H E J O U R N E Y C O N T I N U E S - A C L O S E

elements will remain on Earth.

E N C O U N T E R W I T H S U N - S K I M M I N G P L A N E T. M E R C U RY

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FUTURE; 8.0001 BILLION YEARS

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5

Helium- and hydrogen-burning shells

giant shrugs off its outer layers and becomes aplanetary nebula.

‘helium fuel runs out in the core.

balloon outward, scorching Earth.

In amere 100,000 years, the red

A L L T H AT R E M A I N S A f t e r 8 b i l l i o n

^^years of heat and light, the Sun is now awhite dwarf star, slowly cooling in the depths of space...

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PLANET V

The hunt is on! Space agencies and

astronomers are searching the skies hoping to discover new planets and signs of life... earching for new planets

devoted to locating rocky planets.

around other stars has

With athree-year mission time

become the latest craze in

COROT was “poweredxtpmn

astronomy. New discoveries are announced almost monthly, and

January 2007. The satellite is made

ambitious new missions are tabled

to hunt terrestrial exoplanets (see glossary), specifically those orbiting in the “habitable zone”.

source such as astar.

Switzerland, launched the

This planet-hunting technique relies on the fact that any planet

modern era of planet hunting

M

w h e n h e d i s c o v e r e d t h e fi r s t

extrasolar planet, named 51 Pegasi B, in 1995. His team has now found 100 of

Michael Silionii, COROT This is the zone around astar

passing in front of astar dims the starlight, even if only marginally.

where the surface temperatures of planets could be conducive to life. It is hoped that these missions will not only discover life, but also shed some light on the formation of our own solar system and particularly the development

extremely sensitive, but being in

constellation Libra.

extrasoiar planet.

COROT

In December 2006 the ESA

MISSION

PLANET PIONEER f o u n d t h e fi r s t

removing the distorting effects of Earth’s atmosphere and allowing much clearer sight lines.

searches the universe for other terrestrial

the first space mission specifically

These Include, in 2007, an

Earth-like planet orbiting nearby star Gliese 581 in the

space makes the search far easier,

launched COROT (Convection, Rotation and planetary Transits),

the 270 extrasolar planets known, using the European Southern Observatory’s telescope at La Silla, Chile.

Detectors must therefore be

of life on Earth.

planets.

S TAT S

LAUNCH: 27/12/2006

VMISSION DAYS: 183 to date (25/06/07) %MISSION FIRSTS: first mission with the Iability to locate rocky planets several mtimes larger than Earth.

#LAUNCHMASS:630kg

rDRBITAL ALTITUDE: 896 km

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WMICHEL MAYOR (1942-PRESENT) ichel Mayor, a professor at the University of Geneva,

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up of alarge telescope that detects variations in the intensity of alight

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Michel Mayor

GLIESE 581c Five

times the size of Earth, Gliese 581c is believed

to sustain liquid water on its surface and with

it, possibly life. PLANET

FINDER

NASA's TPF mission

(right) will use an optical telescope

r

and infrared

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array to hunt

5;

distant

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Data collected by the

in the orbit of the local star caused

of our closest stars. SIM will also

satellite is sent back to ■

searching for planets both

receiving stations based

within and outside of our solar

system. Earth-based telescopes generally detect exoplanets using the “wobble technique". This is

in Austria and Brazil to

be processed. COROT

has already surpassed expectations -in May 2007 it;: discovered GJ 436b, aNeptunesized planet orbiting ared-dwarf star, just 30 light-years from Earth It is hoped that this is the first of many ■■■-discoveries — —for COROT. ■

■

where scientists look for awobble

of the Kepler mission will be to gather information on the numbers of Earth-sized planets and their size, and to investigate their stars. The SIM (Space Interferometry Mission) planet quest will conduct agiant census (the first of its kind)

known for his work

■

This new NASA mission

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measure the distances to those

by the gravitational pull of nearby for launch in planets. The bigger the planet, the November 2008. 1 greater the wobble is scheduled

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stars with Earth-like planets.

Both SIM and Kepler will supply information for alater mission, the

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Terrestrial Planet Finder mission

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NASA has three new planned missions, trying to establish

As well as the satellites scanning the skies from space, there are anumber

NASA believes that roughly seven per cent of nearby stars could have alarge planet within a distance equivalent to three Earth-

whether there is life out there.

of active land-based missions. One

The first is Kepler, named after the famous seventeenth-century astronomer. The main objective

team of planet hunters is led by Mike Brown (see box), who is well

m

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orbits. The two observatories aim

to study all the planets outside of our solar system -from their early life, in large dust disks, through to the features of existing planets orbiting far away stars. Back on

■

Earth, scientists will use information

The ofthe planet, fe-^ onnaming September 6, dwarf 2006 came someErie, time after its discovery in 2005. The reason for this delay was largely due to ongoing debate over whether the object was classified as aplanet or aminor planet. Once that issue was resolved the

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Over the next decade, missions

name Eris was chosen. Eris is aGreek

such as the Terrestrial Planet Finder

goddess, the personification of strife and discord. Until then the planet was affectionately known as Xena from the popular TV show, Xena: Warrior Princess The name Eris, in part, reflects

and other planet-hunting missions iwill vastly increase our knowledge iof the stars closest to us and their |:

t h e c o n fl i c t w i t h i n t h e a s t r o n o m i c a l

community over the classification of Eris (and Pluto] as dwarf planets.

on the planets’ complex combination of gases to establish whether they could support life.

TROUBLE AND STRIFE Eris is also known ai

■D i s c o r d i a ” .

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planets. Hopefully they will finally provide an answer to the question of whether there is actually life out there in the vast universe. 11

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G L O S S A R Y

Circumpolar

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stars: Stars that

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the poles tl

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never appear to s e t , but just move around the poles.

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SUN CHAIRS

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patiently for the Sun to rise at

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midsummer to warm their stone cold bodies.

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.theWINGFD

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This constellation represents the flying horse of Greek mythology. It is the seventh-largest constellation, even thpugh

only half the horse is depicted in the sky.

our stars mark out the corners of agiant square that represents the horse’s body. However, one of these stars does not actually belong to Pegasus -Alpheratz is now known as Alpha (a) Andromedae, although it can also be called Delta (5) Pegasi.

S i D E V VAY S S P I R A L

At 40 million light-years from Earth, NGC 7331

is one of the brighter galaxies in this region of the sky. It appears as asmudge of light in asmall telescope.

■ 1

The densely packed globular cluster M15 can be seen through binoculars and small

telescopes, although apertures of 150 mm or so are needed to resolve Its

individual stars. Ml 5lies #

33,000 light-years away. G R E AT S Q U A R E

The Great Square of Pegasus is so large that arow of 30 full Moons could fit within it. Despite its size, the Square contains only ahandful of stars bright enough to be visible with the naked eye. From the corner of the Square marked by Alpha (a) Pegasi stretches acrooked line of stars that delineate the horse’s neck and head, while two lines of stars

extending from Beta (|3) Pegasi trace out the horse’s forelegs. Beta (|3) Pegasi, also known as Scheat, is a red giant that varies irregularly between magnitude 2.3 and 2.7. Midway along one side of the Square lies 51 Pegasi, astar similar to the Sun. In 1995, the first extrasolar planet was discovered around this star. CLUSTERS AND GALAXIES

Near the horse’s muzzle lies one of the finest globular clusters in northern skies, M15, visible through binoculars as arounded misty patch. In the northern

part of Pegasus lies the only other deep-sky object in the constellation within reach of modest amateur

telescopes -NGC 7331, aspiral galaxy presented nearly edge-on to us.

^THE WINGED HORSE

Pegasus was

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the offspring of Medusa the Gorgon. The young Medusa was \ ravished by Poseidon, god of horses as well as the sea. Unfortunately the seduction happened in the temple of the goddess Athene. Outraged at this sacrilege, Athene changed Medusa into asnake¬ haired ogre whose gaze could turn people to stone. In afamous myth, Perseus decapitated Medusa -and

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from her body sprang Pegasus, ahorse with wings. Pegasus flew away to Mount Helicon where he lived with the Muses.

Later he became the mount of the Greek hero Bellerophon.

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'^PEGASUS I

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Pegasus flies high on evenings in October

and November. It is visible from everywhere in the northern hemisphere but from latitudes below about 50° south only part of it can be seen. Pegasus adjoins Andromeda, just north of

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LAGERTA i STEPHAN'S QUINTET At first glance \this looks like asmall cluster of five faint galaxies. However, one of them -at upper right in this image \is actually much closer to us than the \others and lies superimposed by *chance, so the group should perhaps

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EQUULEUS

AQUARIUS

The SUN’S TEMPER TANTRUMS When the Sun breaks out in spots, strange things happen on Earth -or so say asmall group of scientists. Is sunspot activity linked to events on Earth or is it just an odd coincidence?

S

linked with avariety of phenomena. It’s

activity is at its highest. But is it possible that these cooler magnetic sunspots could be affecting us in

been said that they can influence wars,

ways we don’t even know?

the scientific world most of these connections are

SUNSPOTS AND SICKNESS

considered tenuous (at best) or utterly ridiculous.

One theory is that there’s alink between the outbreak of influenza epidemics and the sunspot cycle. According to this theory the flu virus is always present in space, having been left behind in the dust trails of passing comets (believed to be made up of organic material). As Earth ploughs though through these interstellar dust clouds large

ince their discovery, sunspots have been

the stock market, diseases and even fashion! In

^Weknowthatcoronalmassejections(CMEs) Mand solar flares can affect technology both in space

amounts of the virus are stored in our upper

atmosphere. During asunspot maximum, high solar activity bombards the Earth with particles, and sends them raining down into the atmosphere triggering effects such as the northern lights. The same effect forces the virus particles down into the lower atmosphere where they condense into raindrops and fall on an unsuspecting population below.

and here on Earth. As the massive outbursts

FLU BUG Could

of energy speed across space they can render

o u t b r e a k s o f i n fl u e n z a

satellites useless and, as they hit Earth, overload power grids and cause blackouts. It is awelldocumented fact that any spacecraft caught in the firing line of aCME can not only be shunted off course by the power of the solar wind, but

really be linked to the level of sunspot activity?

Sir Fred Hoyle, one time director of the Institute of Astronomy at Cambridge, plotted sunspot maxima against influenza pandemics and found them to be closely correlated. Although arespected scientist, Hoyle’s findings were largely ignored by the scientific community. ALIEN LANDINGS

If the influenza virus comes from space then it is safe to assume that there is life out there. Fred

can suffer serious malfunctions.

Hoyle argued that it is more than likely that life

We also know that these powerful explosions on the Sun happen most at the peak of the solar cycle. Sunspots and solar flares are related to the solar cycle, which runs for atotal of 11 years, going from aminimum -where activity is at its lowest -through to amaximum -where sunspot

evolved and colonised Earth from outer space. So it came as no surprise to him that sunspot activity has been linked with increased alien sightings. At times of intense sunspot action the magnetic field of Earth is buffeted by solar wind and the high-speed stream of subatomic particles that go

i

4

of what he believed to be adistinct connection

between particularly fierce battles and solar flares. Amarked increase in sunspot activity around the

years 1916 and 1917 coincides with some of the

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cruellest battles being fought in World War One

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and the Russian Revolution.

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hand-in-hand with

ROSWELL Did sunspots

CMEs. The massive solar storm of 1989 that

and CMEs force an alien

ploughed into Earth not only battered satellites,

spacecraft to crash land?

0 0

S U N A N D Y O U R H E A LT H

wouldn’t affect alien spacecraft as much as human

Sunspots could also have abearing on how long you live, according to two scientists from Michigan State University. B. Rosenburg and D.A. juckett have suggested that children born to amother who was herself born during aperiod when the sun was at the peak of its 11-year cycle have a

ones. Some say this is what caused the supposed

lower life expectancy,

"UFO crash’’ in 1947 at Roswell, New Mexico.

argument is that when awoman is born her eggs are already formed within her to be released at a

but also caused Earth’s atmosphere to swell. The knock-on effect of increased atmospheric drag on satellites caused at least one to re-enter the atmosphere.

W O R L D AT W A R P e r i o d s

of high sunspot activity correlate with some of the world's worst wars.

There seems no logical reason why these events

While the sunspot phenomenon doesn’t appear to answer the question of whether the object that crash-landed was or was not aUFO, it does

explain how it may have entered the atmosphere.

he reasoning behind this

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later date. If there are alot of sunspots then levels

of radiation are believed to be higher, meaning that her eggs could potentially be dama: :ed. Whatever the truth, scientists and enthusiasts

LINKS TO WAR

ARussian professor of Astronomy and Biological Physics, A.L. Tchijevsky, (see box) became aware

A.L.

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alike will continue to be fascinated by the potential effect of sunspots and the solar cycle on both our planet and us.

(1897-1964)

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chijevsky was convinced that there was aconnection between the outbreaks of war or civil unrest and

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sunspots. To prove his theory he compiled histories of

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72 countries worldwide from 500bc to 1922ad. He

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then compared this data (from as far back as the 17th century when sunspot figures were first accurately recorded) and what he noticed was quite startling. There was adramatic increase in “unpeaceful” events (war and violence) in the five-year period surrounding the solar maximum. Sadly for Tchijevsky he was locked -away for 30 years in Soviet prisons for suggesting that 'this theory may go some way to explaining the Russian Revolution of 1917.

\

\. I. f TROUBLE ON \^

.THE SILENCEO VOICE Many of Tchijevsky's works went unpublished until after his death.

STREETS

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55D KM THICK)

outsized core also helps explain the problems with its crust (see Inside Info box).

rotation. This means that, at the

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much bigger.

may sound like something out of science fiction, but there’s strong evidence for collisions like this

forces that have slowed Mercury’s

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Mercury throughout its history. In human timescales such events are incredibly rare, but over the billions of years of solar system history, they are inevitable and even commonplace.

and there are craters

locked in perpetual shadow, never

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and folds that crisscross Mercury*s

surface form? Experts think that they * V

are created by geological faults. T E M P E R AT U R E C H A N G E S ■

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The idea is that Mercury’s unusually

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large iron core caused the planet to

expand early in its history, cracking the crust apart into separate blocks. Then, as the interior cooled and shrank, the crust collapsed inwards, folding in an effort to fit together. Since there was no way that all the different crust blocks could fit together neatly in the planet’s

RUPES Ascarp

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from top left to

bottom right, cutting through craters.

reduced surface, some parts have popped up in comparison to their neighbours. This happened some time after the heaviest period of impact cratering, since in many places craters and other features continue uninterrupted from one side of arupee scarp to the other.

9

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he final Mariner mission, launched on 3NoveTtrber:

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technique would be able to alter its direction

MARINER II 10REAPED ABOUNTIFUL HARVEST OFNEW

and speed witreut using extra

INFORMATION ABOUT THE INNER PLANETS :

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overcanie the issiii^^ radratioh by constFucting solar panels on an axis As the probe got closer to the Sun the panels were rotated, keeping them at abalanced temperature

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Everything appeared to be going smoothly and Mariner was placed

into aparking orbit for amere 25 minutes: after that it left Earth and

NASA placed the Mariner 10 space probe in an orbit around the Sun, going the opposite way to Earth. This meant the speed of the probe was slow enough for the

Mercury. First mission to explore more than one planet and to return to aplanet for further visits. First mission to use gravity sling-shot and solar wind to manoeuvre. First time TV pictures of Earth seen from space. ORBITAL MASS: 473 9kg

4

vcv GIUSEPPE COLOMBO n9201984) Colombo was G uiseppe invited by NASA*s Jet

Propulsion Laboratory {JPLl to join the Mariner 10 team.

It was his imagination and input that led to the

multiple visits to Mercury. He calculated that by placing the Mariner 10 probe in a specific orbit it would be

“BEPI”

Aplanned European Space Agency

posable to use gravity to bring the probe repeatedly back to Mercury. In total the probe passed Mercury

to be called

aStaggering three t»mes.

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mission to

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that they could use the solar panels on the probe to act as sails. By

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MEMORIES OF THE MOON The surface of

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Mercury showed multiple impact craters, much like the Moon. SAFE STOWAGE

Packed away before launch the Mariner satellite

is carefully

checked over by it^

a

NASA scientists.

aptly named Messenger

^

[1] AN ORIGINAL The modest number of

pictures taken by Mariner 10 were painstakingly patched together by mission scientists. A

NASA-sponsored project is using new technology to smooth out and colour

the original images. [2] CALORIS BASIN

The outer rings of the basin are up to 1 3 0 0 k m i n d i a m e t e r.

The larger impacts created weaknesses

in Mercury's surface through which l a v a fl o w e d .

[3] DEGAS RAY CRATER

The light coloured rays stretching out from the crater are "ejecta" -material blasted away

from the surface by the force of the impact that created Degas.

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Nicolaus Copernicus marshalled all

atechnique called "parallax”, where

the available evidence for aconcerted

acelestial object is sighted from opposite points of Earth’s orbit. We will explore this method later

attack on Ptolemy’s system. Wisely, perhaps, he did not publish his ideas until he was on his deathbed,

but they rightly caused ahuge stir.

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on in the magazine series.

ORIGINAL MAP

Created by hand, this is William H e r s c h e l ' s fi r s t

the gulf of space, they too had to be Suns in their own right. By the late 1600s, scientists such as Isaac

view of the

Newton believed that our solar

Milky Way.

system was adrift in anear-infinite

It soon became obvious that no

KEPLER CRACKS IT

star had aparallax observable by the instruments of the day, which

GALAXIES BEYOND OURS

But, like Aristarchus before him,

meant the stars had to lie at huge

Measuring distances became an

Copernicus could not break from the idea of perfect circular orbits.

distances from Earth. In addition,

abiding passion in astronomy. William Herschel’s early maps of the stars proved that the universe had a“shape”, but

in order to appear bright across

iiTHEHISTORYOFASTRONOMYISAHISTORY OF RECEOING HORIZONS.

I

sea of sunlike stars.

it wasn’t until the 1830s that

J5

telescopes became powerful enough to measure the parallax

Edwin Powell Hubble

and as aresult, his new \BREAKTHROUGHS

"heliocentric” (Sun-centred) theory

WUNIVERSAL EXPANSION

was no better at explaining the motions of the planets. It was not

T

until 1609 that German astronomer

Johannes Kepler described the solar

by Edwin Hubble had two potential

explanations. The first is an update of the old geocentric idea -for

system with its true, elliptical orbits in his laws of planetary motion. Kepler was just in time for the invention of the telescope, which proved the question beyond doubt.

some reason our own galaxy is special, causing everything to move away from it fand on top of that, some mechanism to make the more distant galaxies move away more rapidly). The second is far simpler -the universe (meaning

INTO THE STARS

space itself, not just the objects within

With Kepler’s laws in place, the

it) is growing at aconstant rate and

our galaxy is simply caught up in the general expansion. Because there is

huge scale of the universe began to unfold. The realisation that Earth

made an enormous loop about the Sun gave astronomers the means to measure the distance to stars, using 18

he movement of galaxies observed

|MAIN

knovyn for lending his name to the most famous telescope, Edwin Hubble

measured the distance to farflung galaxies.

more space between the Milky Way and more distant galaxies, they move away more rapidly.

I

of distant stars. As telescopes grew in size and long-exposure photography became even more powerful, agreat debate raged about the nature of the strange “spiral nebulae” in the night skies. Some astronomers thought they

brought another shock. Hubble

noticed that nearly all the galaxies seemed to be moving away from us, and the more distant they were, the faster they were retreating. The only convincing explanation for this discovery was that the universe was not the static place

were young solar systems in orbit

every direction bears the faint afterglow of this moment. The radiation is very weak, and warms space to just 2.7 degrees above absolute zero, but it can only

have come from the Big Bang.

that most scientists had assumed,

of distant galaxies, we now have an idea of the age of the universe.

but was instead expanding rapidly. And most people agreed that if it

ago, the Big Bang is surprisingly

of innumerable stars -in fact,

galaxies in their own right.

was expanding, the entire cosmos must once have been compressed to asingle point in space and time

E X PA N D I N G H O R I Z O N S

-what we now call the Big Bang.

1924 when Edwin Hubble carried

AN ALMIGHTY BANG

out the direct measurement of star

D E E P S PA C E

distances in the spiral nebulae (distant galaxies), and proved that such objects were, in general, many

Snapped by the

millions of light years away.

This discovery showed that the universe was vastly bigger than had ever been imagined, but it also

Occurring around 13 billion years

> I

times the age of our solar system. But while cosmologists think they now have apretty good idea of our true place in the cosmos, they

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instance, there could well be

image of the

refining their measurements of

hidden dimensions, or other

galaxies beyond ours

the rate of expansion. The clinching

universes alongside our own. Whichever way the wheel turns,

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that this is the last word. For

proof that the universe was formed in agreat explosion came in 1965, with the discovery that the sky in

the universe.

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evidence for the Big Bang, and

immensity of

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would be unwise to think

shows the

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“recent”. To put it another way,

Cosmologists have spent much of the twentieth century finding

Hubble Space Telescope, this

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close to the Milky Way. Others believed that they were vastly more distant and composed

The debate was finally settled in

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another revolution in our view of the cosmos is almost inevitable.

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MERCURY TRANSIT This picture of the Mercury transit of 2006 shows the planet as aclear dot against the fiery background of the Sun.

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01/04/2013

his Mercury locator chart [left] shows the planet’s motions through the sky over the

coming years. The winding line shows Mercury’s j

16/08/2012

05/12/2012

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9 !

changing position relative to the Sun (centre line). The shading indicates the extent of the

dawn/dusk sky around the Sun, revealing that Mercury rarely makes it out of the twilight into the pre-dawn or post-dusk sky. The best es

to

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VULCAN -the HIDDEN PLANET Supposedly situated somewhere between Mercury

and the Sun, Vulcan became the astronomical Holy Grail of the early nineteenth century. oday, the planet Vulcan is best known as the closer to home, there was asimilar mystery. We home of Star Trek's Mr Spock, but in the late now know that Mercury’s orbital “wobble” is a

URBAIN LE VERRIER

This science grandee is one of 72 people whose

nineteenth century, many astronomers

names are engraved upon the Eiffel Tower, for their

outstanding achievements.

thought it was areal world -atiny, burned world orbiting closer to the Sun than Mercury. The saga of Vulcan began with the French

result of general relativity -the distortion of space itself caused by the great mass of the Sun -but in Le Verrier’s time, an additional inner planet se e me d th e o b vi o u s so l u ti o n .

astronomer and mathematician Urbain Le Verrier.

The new planet would be so close to the Sun that it would only be revealed during total solar eclipses -otherwise it might be seen as adark iiIHAVELOOKEDFORTHERINTO spot when it crossed the SPACE THAN EVER HOMAN OEING

Though he seldom looked through atelescope. Le Verrier made his

name for his precise understanding of orbital dynamics, and the way that each planet's

gravity affects the

face of the Sun in a

DID BEFORE ME VUiiliam Herschel

motion of the others.

transit”. In 1859, Le Ve r r i e r r e c e i v e d a l e t t e r from Edmond

Lescarbault, aFrench amateur astronomer, who

In 1846 he sealed his place in the history books with claimed to have seen just such an event. From his accurate prediction of the position of Neptune accurate that the astronomer following his calculations found it on his first night of searching. s o

The discovery of Neptune was due largely to [explained “wobbles” in the orbit of Uranus, at the Jextreme reaches of the known solar system. But

Lescarbault’s observations, Le Verrier calculated an

orbit for the new planet, which he named “Vulcan after the Roman god of fire. Vulcan was excitedly discussed by astronomers as they prepared to observe the solar eclipse of 1860

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SOLAR SYSTEM F E AT U R E S ^YOUR SOLARSYSTEMMODEL Use your model to see how the inferior planets have unique patterns of movements in Earth's sky.

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SOLAR SYSTEM GUIDE Our nearest planetary neighbour, Venus is Earth's evil twin, with adevastatingly hostile atmosphere.

MISSIONS Launched from the shuttle, the Magellan probe mapped the surface of Venus in amazing accuracy.

Infrared and radar imaging from Galileo and Magellan reveal fascinating details of Venus through its clouds.

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with care to prevent damage to its parts, and stored or displayed safely to ensure no parts aw4ost. !htever use liquids or solvents to clean the parts. For best care, use the polishing cloth and dusting brushes supplied^ith the toolkit (free to subscriptions customers). !When assembling parts, iajrthem-on-a flat table and keep screws and alt small items on atray so th^ can't roll away and get lost. Unpade afl parts carefully. !The pubiidier reserves the right to \alter parts and thefr design at any time.

!The publisher cannot replace any parts that are damaged or tost by the . customer wHUbut ^arge. !The pufali^ier caimot be reaponsible for any damage that may occur as a result of incorrect assembly or mishandting^pf theonety-Please ensure you read the instructions thoroughly «d*en assfflnblmgJfre parts. !>U! tools must be uc^ with care, folbwing any safety guidelines provided by die manufacturer. !The publisher cannot be responsible for ar^ usuries caused by any tools or materiats.

Venus is the easiest of all planets to see, shining brightly as the morning or evening "star".

UNEXPLAINED

CREDITS

In the 17th and 18th centuries, astronomers were

fooled into thinking that Venus had its own moon. C O N S U LTA N T E D I T O R : G I L E S S PA R R O W

ENDORSED BY: SIR PATRICK MOORE CBE FRS

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'Pantheon Egyptien: collection des personnages mythologigues de i'ancienne Egypte' by Jean>

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11 (t) Corbis UK, (br) NASA; 12-13 NASA; 16(cr) Ancient Art 8c Architecture Collection, (b)

Museum of Art, New York, USA,

Corbis UK/Roger Wood; 17(t) Topfoto/British Museum, (b) Art Archive; 18(t) Corbis UK/Nick Wheeler, (b) British Museum; 19(t) Werner Forman Archives, (b,c)

AKG London; 20 Galaxy Picture Library/Robin Scagell; 21 Courtesy

Charles Edwin Wilbour Fund/The

IBridgemanArtLibrary,(br)NASA. ARTWORKS: 5(tr) Eaglemoss Publications; 5(c), 9, 14-15, 22

Pikaia Imaging. REPRO: Stormcreative

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NFERIOR

E V E N I N G S TA R

In spring and early

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to the Sun than Earth. This gives :Jie maunique pattern of movements Earth's sky, which your solar system I

model is designed to reflect.

nterms of their orbits, the planets of the Solar System have long been split into two distinct

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groups -inferior planets with orbits that are

inside Earth’s, and superior planets with orbits that are outside.

Whether aplanet is inferior or superior has a huge effect on the way it moves when viewed from Earth. Superior planets make long, relatively s l o w circles (with some complicating loops) that can carry them all the way around the sky and deep into the nighttime constellations that l e

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directly opposite the Sun. -X)

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Inferior planets i n contrast, make rapid loops away from the Sun and then back towards it as if

tethered by invisible elastic. They seldom get far enough from the Sun to appear in atruly dark sky instead we see them as permanent residents of the morning and evening twilight. The way these planets move has even influenced their names

Mercury, Which can only ever be glimpsed for afew nights at atime, is named after the fleet-

footed mg||enger of the Greek gods, while brilliant Venus is s'oi i^es known by the alternative names of

evening*^sfars.

rand Hesper, the morning and

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G L O S S A R Y

Degree: Ameasurement of angle in the sky. There are 360 degrees in a circle around the entire

horizon, and 90 degrees from the horizon to the

point directly overhead (the zenith).

to the Sun we can see their entire orbits abit like

an edge-on dinner plate. Venus’s orbit covers 93 degrees of the sky (see Glossary) so even when the planet lies on the outer edge of its orbit as seen from Earth, it is never more than 47 degrees from the Sun. For Mercury, the situation is even more extreme -at best it can reach amaximum of 28

degrees away from the Sun, so it is only ever seen against fairly bright skies.

LOOPS IN THE SKY

Acomposite photo of Venus's path, clearly showing how you can view the entire orbit of

an inferior planet.

or Venus year for them to return to the same position relative to each other.

In general, Venus returns to the same location relative to Earth every 584 days, and Mercury does the same in 116 days. SHIFTING PHASES

Inferior planets have one other important difference from the superior worlds -they show

phases (see Glossary) similar to those of the

SIGNIFICANT POINTS

Moon. These arise because our changing point of view allows us to see different proportions of the

During each orbit around the Sun, an inferior

planet’s daylight, sun-facing side at different points

planet passes through anumber of significant points in its orbit called conjunctions and elongations (see Conjunctions and elongations). Because these points depend on the relative positions of Earth and the inferior planet, and both worlds are moving, it takes longer than aMercury

in its orbit.

When it is on the same side of the Sun as Earth,

the planet will appear to have the largest diameter, but most of its sunlit side will be facing away from Earth and towards the Sun, so it will display a

crescent phase. On the far side of its orbit relative

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The overhead provided your solar view system model by makes it easy to tell where aplanet lies in space compared to the Earth. Inferior conjunctions take place when the planet lies in between the Earth and the Sun, and superior conjunctions when the planet is on the opposite, or farthest, side of the Sun from Earth.

At other times, if aline from the

planet to the Earth has the Sun on its left, the planet is to the west of the Sun and rises ahead of it in the

morning, while if the line has the Sun on its right, the planet is east

of the Sun and setting behind it in the evening sky. Sonne orreries use alightbulb to represent the Sun. In this case, you are able to view the rising and setting and waxing and waning of the planets quite clearly. By advancing your model’s motor slowly and studying the angle between Sun, Earth and planet, you can identify the points of greatest eastern and western elongations. Allowing the motor to run in this way will even work out the visible phase of the planet (see

Superior

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Phases below].

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to Earth, the planet will be much more distant, but

shows why you see changing proportions of

an observer will be able to see more of Venus’s

Ve n u s ' s f a c e i n a s i m i l a r

daylit side, so it will appear “gibbous”, with a

way that you do with the

phase between half and full.

face of the Moon.

VIEWING VENUS

Inferior planets are typically at their most

brilliant in the sky about halfway between their greatest elongation and inferior conjunction (see Conjunctions and elongations), when the proportion of the daylight side visible and the planet’s relative closeness to Earth combine to

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maximum effect.

^GLOSSARY Phase: The amount of

daylit surface of the planet or moon visible to t h e o b s e r v e r.

Tracing the changes in their phase, size and apparent brightness (which is most easily done with Venus) is afascinating study for anyone with asmall telescope or even agood pair of binoculars (7x50 or 10x50 will be ideal).

INSIDE lIMFO

C Q N J U N C T I O N S A N D E L O N G AT I O N S

\jhen aplanet lies on the far side of

the face of the Sun. When they do, the event

superior conjunction, and when it is on exactly

Some way to the east and west of inferior conjunction lie two other special points known as the greatest eastern and western “elongations” -these are the points where the angle between the Sun, Earth and the planet is at its greatest, so the planet is at its greatest distance from the Sun in the sky. At this point, you will have the longest time

tthe Sun from Earth, it is said to be at

the same side of the Sun as Earth, it is at

inferior conjunction (a conjunction is simply a coming-together of two objects in the sky as viewed from Earth).

Although when seen from above (see Phases) the inferior planets appear to lie directly between the Sun and the Earth, In reality Venus and Mercury rarely pass across

is known as atransit.

to see it before sunrise or after sunset.

61

[6] DESCENT THROUGH THE CLOUDS This artist's impression shows the Soviet Venera 7probe parachuting through the sulphur clouds of Venus on 15 December 1970. Rapid descent through the upper atmosphere helped to slow the egg-shaped titanium capsule to asteady 14

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Morning elongations follow about five months after evening ones, as the planet passes between the Earth and the Sun (pictured). But nearly 15 months elapse between evening and morning elongations because Venus has

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PHASED IN

Like the moon, Ve n u s s h o w s

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Solander stands in the background ready to record the event. To avoid being blinded by the Sun, the trio viewed the transit through coloured filters -amethod not recommended today! The stamp was issued by Tuvalu, aPolynesian island in the Pacific, to mark the bicentenary of the explorer’s death.

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SOLAR SYSTEM F E AT U R E S YOUR SOLAR SYSTEM 30

I M P O R TA N T m !The orrery Is aprecision-engineered kit. it must be assembled and handled

MODEL

Complete the assembly of Stage 2Phase 1and take acloser look at how the engraved gear will be used.

0

SOLAR SYSTEM GUIDE Explore the surface of Earth's nearest neighbour, Venus, where laval plains surround soaring volcanoes.

EMISSIONS

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121

16

20

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During the Soviet vs American space race, Venera probes gathered remarkable data about Venus.

IMAGE GALLERY Three-dimensional imagery and electronic colouring provide specular views of Venus's landscapes.

THE STORY OF ASTRONOMY From the 6th century bc, Greek scientists started to apply mathematics to astronomical observations.

S TA R M A P Recalling Greek legend, Pisces is seen as two fish swimming in opposite directions, joined by acord

UNEXPLAINED An occasional glow, the ashen light on the night side of Venus has stirred much debate among astronomers. C O N S U LTA N T E D I T O R : G I L E S S PA R R O W E N D O R S E D B Y : S I R PAT R I C K M O O R E C B E F R S E N C O U R A G E D B Y: T H E I N T E R N AT I O N A L A S T R O N O M I C A L U N I O N

■■ I I

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^University; 5(c,b) NASA/JPL, (t) 'NASA/Thierry Lombry/APOD; 6 NASA/JPL; 7Galaxy Picture Library/ JPL; 8(t,c) NASA/JPL; 9{t) NASA/ NSSDC, (b) NASA/JPL; 10(t,br) NASA/NSSDC, (bc) Corbis UK, (cl)

mTopfoto; 11 (tl,tr) NASA/NSSDC,

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Keep out of reach of children. Keep this Information for reference. Applies to all issues of 'Build AModel Solar System'. ©Eaglemoss Publications (2008). All rights reserved. 2

1

COMPLETE Stage PHASE 1

O PD CO

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LO

■
surface. This may be significant as such storms often happen above active volcanoes for reasons

scientisis still don’t fully understand, The European Venus Express orbiter also detected lightning high in the atmosphere. More intriguingly, spacecraft have discovered that amounts of sulphur dioxide gas in the atmosphere vary alot from year to year, suggesting that active volcanoes occasionally pump out fresh supplies that then gradually dwindle away.

and creating pressurized chambers of molten

H

G) d

o

years. As the centre of Venus gradually cools and pumps out less heat, they wi! b e c o m e

magma across much of the planet. When the pressure finally gets too much, Venus "blows” ~

frequent, but there is no reason to believe that

the magma forces its way out through any weak

we have seen the last of them yet. One day the

spots it can find, and over afew million years,

volcanoes will re-awaken and flood the low-lying

it spreads out across the planet, obliterating everything in its wake and eventually setting to

regions, reshaping the planet once again and

leave a

LD

wiping out the Venus we know today.

pristine new landscape,

COOLING DOWN

The last time this happened was 500 m i l l i o n years ago, and only afew highland areas, such

Alpha Regio, survived relatively unscathed bearing the only remnants of amore ancient a s

Venusian surface. These cataclysmic eruptions

probably happen every few hundred million

accumulated. Even though Venus’s thick atmosphere shields the planet from most space debris. afew meteorites do make it

through -more than 1000 have now been counted. From studies of the Earth and

Moon, scientists have apretty good idea of the rate at which such impacts happen in our part of the solar system, and it seems to have been steady for the past 3billion years or more. So, the older asurface is, the

4

V E N U S T O D AY

New impact craters have formed but internal pressure

builds up again -ready for the next violent eruption.

more time it has been exposed to bombardment, and the more heavily cratered it will be, on average. Volcanic eruptions and other events can effectively wipe asurface clean, resetting this crater “clock”.

C R AT E R D AT I N G Regular lava flows scour the surface, so only recent meteors have left amark.

I

Ve n e r a s 3 t o s i m i l a r ^

,IThis 2fo-taH;

featuring a a n i s ; : spimrifiil eMry ):arO^T^

f r .

S’©

Qn 18 Oct^r 1967, Vetrera

etw^h 19^1 and 1984,

and Venera 2, launched as with all

became the fir^ spacecraft to JH

the USSRsfi^ aseries of

of ^craft as part of apair, lost

measuretieainjsphereaniillWr»ii|TiiBBaa^tiwg^v.^

communi^tions just-before

realised that their chicles’

ronSS .

eaned Venera (the f o r Veeus) to piber data from Venus.

atmospheric aitry. Abreakthrough came, however,

hulls, designed to withstand 25 solar panels and

The initial missions were dismal

with its twin, Venera 3. Launched

atmospheres, would be crushed ^dish antenna. .^

failures. Venera Iwas lost on

on 16 November 1965, it became

route, Veneras 1964A and 1964B

the first manmade object to land, albeit with acatastrophic crash

didn’t reach their parking orbits S PA C E

S TA R S

WSERGEI PAVLOVICH KOROLEV (1907-1 gee)

Korolev widely is regarded as one of the founders of the

Soviet space programme. His first involvement with rockets was

during the build-up to World War II. Following imprisonment, along with many colleagues, under Stalin, he quickly rose to become t h e h e a d o f t h e fi r s t S o v i e t r o c k e t

development centre, known now as RSC Energia. His greatest achievement was to turn rocket weapons into the basis of aspace exploration programme -afeat that ensured that the Soviet Union would be the

world’s first space-faring nation.

10

pisiet. The Scoffit Space authoriti® Teok^i^^i^cal

'gl¬

1

F

VENERA 7

The 1m,

500kg, egg> shaped landing capsule was

parachuted to the surface o f Ve n u s o n 15 December 1 9 7 0 .

< m

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bytile75-100a^mi^pheresbnthe surface of Veaus and launched bothj U t e i t s t w i n , : I' i .

Venera 5and 6as^nospheric .^probefe They recorded 53 and :^^; 51 minutes

image captured by NASA's Aqua satellite on 2August 2006 shows

two large fires (marked red) in the Okanogan-


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00

[5] BLUE MARBLE IInspired by the famous photograph of planet Earth taken by the crew of Apollo 17, this image is the most detailed true-

colour image of the planet to date. It is in fact acomposite image, created at the NASA Goddard Space Flight Center. Most of the information

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arly Earth had an atmosphere that

E was

dominated by carbon dioxide, similar to the atmosphere of Venus. Early, one-celled life-forms -bacteria or prokaryotes -were the first organisms to

develop photosynthesis. This, it is argued Eby some, would have been able to produce an oxygen-rich atmosphere, capable of

r

Sunlight

O

HaO +COs +Rlutrients

L Water ^Carbon h d i o x i d e .

( / )

^3:

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matter

N i t r a t e

Sugars

+O2 Oxygen

Phosphate

supporting more advanced life-forms.

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1

around the vents. The most primitive bacteria

areas of shallow water the mats started to grow

on Earth today are also tolerant of intense heat, suggesting that the first bacteria evolved in searingly hot conditions such as those close to early black smokers. Whether it was generated in sea vents or soupy pools, the earliest life would have been chemosynthetic -using chemical reactions to release energy. But at some time before 3.4 billion years ago (according to the earliest fossils found), ashift to photosynthesis (see How It Works) changed everything. Cyanobacteria began to use sunlight energy to convert the abundant carbon dioxide and water to make organic food, producing oxygen as waste. This oxygen then

into grouped globular shapes. This was the first ever ecosystem ~the bacteria on the surface had a different role from those in the centre.

X m Amino add: Abasic

building block of protein, which is present in all lifeforms. Some have been

O O

found in meteorites, which

COMPLEX LIFE-FORMS BEGIN

The changes brought about by these living rocks were far-reaching. Over the next two billion years

has prompted the

suggestion that life may

o

have arrived on Earth from

T !

an extraterrestrial source. T l

the bacterial clusters raised the oxygen levels in

the atmosphere to 20 per cent, creating intolerable conditions for organisms that liked carbon dioxide. Some died out; others adapted and survived.

It was in this period that the shift from singlecelled to more complex organisms took place. Around three billion years ago, one kind of

ROTIFER An example

of complex multi-celled life that developed over

three billion years ago.

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COMET One theory /

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holds that life came to Earth on acomet from elsewhere in the u n i v e r s e .

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of the lunar orbit and the related fact that Earth’s

we have to look way out beyond Neptune, into the icy depths of the Kuiper Belt, where the demoted dwarf planet Pluto and its major moon Charon are even closer in both size and separation.

rotation is gradually slowing down (so that aday

R E L AT I V E S I Z E S Moon's size and distance from Earth -to scale.

THEORIES OF LUNAR ORIGIN The Moon, then, breaks alot of the rules about

planet formation

SO where did it come from?

now lasts two hours longer than it did about 600 million years ago). According to this idea, the Earth had spun so fast in its youth that it became unstable, flinging off material from its bulging equator that went into orbit and coalesced to form

the Moon. Some even suggested that this event MOON

SHADOW

For along time, three different theories vied for

Farmers have long relied on the Moon to light

supremacy. The simplest was that the Moon

their nocturnal labours.

formed the Pacific Ocean basin. But it soon became clear that Earth could

never have spun fast enough for this scenario.

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and eventually, evidence brought back from the Moon by the Apollo missions backed up afinal, cataclysmic theory that is widely accepted today

WAXING

Most significant of all, though, the Moon raises tides on the surface of the Earth. Tides are bulges in the Earth caused by the pull of our satellite’s gravity. They distort the shape of the Earth itself, creating abulge directly beneath the Moon, and acounterbalancing bulge on the other side of the planet (in reality, the bulges are slightly offset because of the Earth’s fairly rapid rotation).

MOON

The phases of the waxing (growing) and waning M o o n a c t a s a c a l e n d a r.

-the so-called Big Splash (see Breakthroughs). REMARKABLE POWERS

Some 4.5 billion years may have passed since its formation, but the Moon has not been amere

passive observer of events on Earth. Even in a modern world that protects us from many of the

GLOSSARY

INFLUENTIAL PARTNERS

Dwarf planet^^s

The Earth’s surface is largely covered by alayer of water that is much easier to pull around than its

forces of nature, we are still subject to its effects in our everyday lives.

HTilil

interior rocks. Because of this the tides have the

For our ancestors, the Moon was of crucial

importance -the changing cycle of its phases regulated calendars as far apart as Mesopotamia and Mesoamerica, and in an age before artificial lighting, full Moons allowed harvesters and hunters alike to continue working beyond sunset.

Asteroi

greatest effect on our planet’s oceans, causing them to rise and fall to amuch greater extent than the Earth’s land surface as the planet effectively rotates beneath the two tidal bulges. The complex daily and monthly cycle of tides is acombination of influences

^HOW IT WORKS

^TIDAL CYCLES coast on Earth experiences E very aday, caused by the pull of the

high and low tides twice Moon. This takes the form of atidal “bulge”, with shallower water in between

bulges. The cycle repeats 40-50 minutes earlier each day. Meanwhile, throughout the month, the tides run twice through acycle that ranges from the extreme highs and lows of “spring” tides, to shallower “neap” tides, and back. The day-to-day change is caused simply by the changing direction of the Moon as it orbits Earth in just over 27 days. The cycle of spring tides and neap tides, meanwhile, is aresult of the changing directions of the Sun and Moon. Although the Sun is much farther away from the Moon it is also much more massive and so its gravitational pull raises its own tides on Earth. When these are lined up with the lunar tides (around new and full Moons), the changes are particularly extreme. Midway between these times (around the first quarter and last quarter), the solar tides counteract the lunar tides, flattening out the bulges. SPRING AND NEAP TIDES

The tides on Earth are at their highest when the Sun and Moon are in alignment. As the Moon moves round the Earth it counteracts the Sun's pull and the tides diminish.

spring tide gravitational forces of Sun

and

Moon

combine

to create highest tides

tides

are

when

Sun

Sun’s

i n fl u e n c e

wanes

as

moves

around

lowest and

Moon

are at right angles

t neap tide

Moon Earth

SOLAR SYSTEM GUIDE Othe double planet

LUNAR As our closest neighbour in space, it is hardly surprising that the Moon has been the target of the majority of remote interplanetary missions. he earliest missions to the

The

Moon were the result of

intense activity by both the

USAand the USSR to develop rockets capable of delivering nuclear warheads from one continent to

"41

containing a

anotfier. Fortunately, while the politicians postured, they also budgeted generously and the so-called

r o c k e t m o t o r.

space science and technology. The first US probes to the Mooi

1 t i

were the Pioneer series. Pioneers

part of 1958. White they all failed in their mission to photograph the Moon close-up, they did travel BREAKTHROUGHS

^ION PROPULSION nSeptember 2003, the European Space Agency launched a revolutionary probe which took almost 13 months to reach the Moon. Its name was Smart-1 and its rocket motor ~having less power than apuff of breath was an early space trial of asolarpowered ion engine. While astandard chemical rocket can operate

only in bursts before its fuel runs out, an ion

engine can burn continuously for years. Once in lunar orbit, the

probe mapped the Moon with X-rays, specifically looking for frozen water at the south pole. It was deliberately crashed into the lunar surface in

September 2006, having generated much useful

|| data that will be put to t o M e r c u r y.

on the Van Allen radiation belts that

would prove extremely useful to subsequent missions. Pioneer 4, which was launched on 3March 1959, also failed, of more than 60,000km. like the

to 3were all launched in the fatfer

iuse in planned missions

far enough to provide data on the space between Earth and its satellite, including new information

missing the Moon by adistance

space race saw huge strides place & i n

99kg soft-landing lunar capsule. pictured in front of the complete. 1580kg spacecraft.

S M A RT- 1 A n a r t i s t ’s i m p r e s s i o n o f E S A s i o n -

powered spacecraft on its Moon mission.

former spacecraft, it too ended up in an orbit of the Sun.

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LUNAR ORBITER This programme consisted of five identical 390kg

SURVEYOR 3This, the third of the US Moon lander series, was the first to

spacecraft. Their mission was to

feature arobot scoop. This was used to help analyse the fine surface soil.

photograph lunar landing sites.

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Between 1961 and 1965, the USA

launched the Ranger series of probes. All except Rangers 7to 9 suffered from technical problems. The probes were designed to send back live images of lunar surface as they headed fee^nlmpact with the Moon -andThis the last three

did, with considerable success,

returning thousands of images.

and relaying them back to Earth, The Soviet space agency then deliberately self-destructing on followed asimilar course to MASA ■I: the lunar surface.

Having gathered enough data to choose alanding site, NASA

1967, succeeded, taking images

mail

[iiaim

pictures on the way. Luna, i, ^ugh, mi^d and whether the lunar surface was became the first spaeecT^ in able to support alanding vehkle. solarcHtritiR lPS^. Uina 2. which Seven spacecraft were launched followed shortly afterwards, brame and all except Surveyors 2and 4 the first craft to impact on the lunar succeeded in making asoft landing. surface, and its sister probe, Luna 3,

The next series of US lunar

five, launched between 1966 and

s

scientists now wanted to find out

■h

took the first pictures of the far side

probes, the Lunar Orbiter, was

designed to orbit the Moon and photograph areas that were being selected as possible landing sites for the manned Apollo missions. All

designing ajKobe initially to otsW land bn the Moon wtitfe reSirning "I

I

of the Moon.

Not only did the probes take thousands of photographs but

When, in 1969, the USA landed aman on the Moon, the Soviets

Surveyor 3analysed asoil sample.

continued with unmanned missions device to measure

The 1968 Surveyor 7mission was purely scientific, exploring the u n a r region around Tycho crater.

up until 1976. Luna 24 was the last j Soviet mission to date, returnin

soil samples to Earth for analysis.

Surveyor 5had an alpha-scattering the abundance

of the major elements of the lunar surface.

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LUNAR FEATURES Because it lies so close to

Earth-tied observers, no other

heavenly body in the universe can be seen in so much detai

and so easily.

D the Moon and, unless it’s showing its full oint atelescope or apair of binoculars at

face, the light of the Sun will shine across the surface, revealing the many dramatic features. Acasual glance shows that the Moon is covered with craters, which are the scars of ancient

asteroid impacts Look alittle longer and you will be able to see mountains, ridges and the vast, sunken plateaux that astronomers call mares, or seas. Every night

as the Sun shines at different angles, you will be able to see their changing appearances.

[5] GIANT IMPACT HYPOTHESIS Apopular theory for the formation of the Moon is that the young Earth was struck by aMars-sized body, Theia, named after the Titan of Greek mythology who gave birth to the Moon goddess Selene. Theia may have been in the same orbit as 1

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Earth and about 60° ahead or behind. As it grew its angular distance from Earth fluctuated until the two collided. Theia's mantle and much of Earth's mantle were ejected into space and Theia's core sank into the Earth's core. The orbiting debris later coalesced to form the Moon.

PATRICK MOOR UNAR V STON

'.in 1;

The legendary Sir Patrick Moore selects 10 lunar history highlights -some from the earliest days of astronomy, others from recent times...

W

FA R S I D E I n

of observation and

1959, Luna 3sent b a c k t h e fi r s t

discovery, it was quite achallenge for Patrick Moore to select just 10 milestones in the Moon’s story. It was bound to be a

images of the far

back valuable data -for instance,

TO THE MOON

confirming that the Moon has no detectable overall magnetic field.

In 1968, Apollo

Luna 2landed, although it impacted and presumably broke up. No signals

side of the Moon.

partly personal choice and he

were received after

began with the telescopic observations of Galileo (see Breakthroughs, page 19). Indeed, his first five milestones were during

touchdown.

the 17th to 19th centuries. Then in

8became the fi r s t m a n n e d mission to

4

journey to the Moon and back to Earth.

♦ I FA R S I D E ^

IInOctobercameLuna ,^3, which went round

*

^

the

Moon

and

sent

back the first images of ■HHHi the far side -those areas which are always turned away from the Earth and which we can

never see. Speculations had been

rife and it had even been suggested that all the air and water had been

drawn round to the far side, which

might, therefore, be inhabited. Luna 3disposed of all these ideas.

The images seem very poor and the 20th century space flight took off and lunar discovery advanced in leaps and bounds. In 1959, the Soviet Union's Lunas

blurred by present-day standards, but Luna 3was atriumph. It was

LANDING The

first landing on the surface of the

confirmed that the far side is just as cratered and just as barren as the hemisphere we have always known.

Moon was by the USSR's Luna 9.

1, 2and 3were the first spacecraft to be sent to the Moon. Luna 1

by-passed the Moon and sent

But the only large “sea” is the Mare □

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ith such arich history

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O Orientale, atiny part of which can

CREW James

Surveyors, of which five were

Apollo 10, crewed by astronauts

be seen from Earth under the most

Lovell, William Frank Borman

successful. The following year saw the first successful Apollo flight

Thomas Stafford, John WYoung

favourable conditions.

-the astronauts

to the Moon. In December 1968,

who manned the

Apollo 8, carrying astronauts Frank Borman, James Lovell and William

The Russians also mapped the “Soviet Mountains”, which they

believed to bepf great importance, but which were later found to be

nothing more than abright ray.

Anders and

Apollo 8flight. EAGLE The Lunar

Anders, made acomplete circuit

Module (above

and paved the way for alanding.

centre), moments

"CONTROLLED LANDING In 1966, the first successful

^controlled landing on the Moon

was made by the USSR’s Luna 9. It

after separating from the Apollo

There had unquestionably been a

Module.

“space race” between the USA and

Apollo 13 mishap.) On 19 July 1969, Neil Armstrong then Buzz Aldrin stepped on to the

SMALL STEP

USSR, and the Americans won. The Soviet rockets were not reliable

rocky surface of Mare Tranquillitatis. The gap between the two worlds

enough, and after one particularly disastrous explosion the Russians

had finally been bridged.

Buzz Aldrin's

Procellarum and sent back images

footprint (above

direct from the surface. These

right) -barring an Impact, it will remain intact for

millions of years.

o >

m C O

H

O m C O

THE ELEVENTH MILESTONE

gave up.

In 1969 -the year of “the

Patrick Moore planned to end his

highlight of all highlights” -Man

personal selection of lunar highlights with Armstrong’s “one

reached the Moon. In May,

that the maria, at least, were

-
1839 Publication of the

4^ 1610 Galileo’s telescopic

H

observations of the Moon. He

great work Der Mond by

was not the first to do so

Wilhelm Beer and Johann

O

(Thomas Harriot was), but he was more systematic, and he produced amap showing

H e i n r i c h v o n M a d l e r.

7D


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introduced the system of

naming the craters after famous people -usually (but not always) astronomers. His system is still followed, although of course postRiccioli astronomers come off second-best, as the main features of the Moon had

already been named.

GALILEO In 1610, the great Italian astronomer published detailed drawings of the Moon in his Siderius Nuncius

[Starry Messenger)

41778 First observations by Johann Schroter, who made

detailed drawings for over 30 years. Unfortunately he never made afull map, and his observatory, with all his unpublished observations, was

WILHELM BEER The Berlin banker who

destroyed by invading French

Der

soldiers in 1813.

in

In 1998, another probe,

Prospector, was deliberately crashed into apolar crater in the hope that water would be found in the debris flung out. The results

set up aprivate observatory and co-authored Mond

1839.

41852 Warren de la Rue took some photographs of the

O

Moon. He was not the first to do so, but his images

z

represented amajor advance. By the end of the century the first photographic atlases of the whole visible surface had been produced.

41866 Announcement by JSchmidt of the Athens Observatory that the crater Linne, on Mare Serenitatis. had disappeared, to be replaced by a

white spot. We are now certain that there is no real change but the announcement caused a reawakening of interest in lunar observation. Many people had thought that the map by there was little point in continuing I From 1890, when the British

m C O

H

iits Lunar Section, the Moon has been under constant scrutiny.

o

POONBASE Both Russia and the USA have plans ~such as this one -but no-one knows when the fi r s t w i l l b e r e a l i s e d .

no skating rinks on the Moon! W H AT T H E F U T U R E H O L D S In the future there must be another

highlight -the official opening of the first Lunar Base. When this will

Time will tell!

>

\Astronomical Association founded

existed there, he reckons. There are

there to see it. 2030? 2050? 2080?

0

B e e r a n d M a d l e r w a s s o fi n a l t h a t

were negative. Patrick Moore is acomplete sceptic about this -water has never

happen, Patrick does not know, but it ought to be within the next few decades, in which case many of you now reading these words will be

O I

A ' - T ' i -

m CO

ARIES and TRIANGULUM Aram with agolden fleece graces the evening skies at the turn of the year. It is called

i

Aries, and next to it lies the

northern triangle, Triangulum. "a*

A

""

ries is one of the less prominent figures of the zodiac but is of considerable astronomical

significance. In the time of the Greek

astronomer Hipparchus, in the 2nd century bc, the point at which the Sun crossed the celestial equator from

"-P Y-

south to north on its annual path around the celestial sphere lay in Aries. This crossing point -the vernal equinox -now lies 30 degrees away in neighbouring Pisces, because of the Earth’s toppling motion (called

RAM HEAD

'Alpha (a), Beta (p) and Gamma (y)

precession). But this point is still referred to as the

Arietis form the

First Point of Aries.

head of Aries.

Aries is most easily recognized by its crooked line of three stars. Alpha (a). Beta (p) and Gamma (y) Arietis, which mark the horns and head of the ram. The rest of ■' i t

^CTLCENFLEECE ries represents the ram of legend that was clothed in golden wool. This ram could fly, and saved Phrixus, the son of King Athamus of Boeotia

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w h e n h e w a s a b o u t t o b e s a c r i fi c e d to avert afamine in his father’s

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land. With Phrixus on his back, 4 sf

its body is outlined by much fainter stars. Alpha Arietis is an orange giant of magnitude 2.0. The faintest star of the trio. Gamma Arietis, is an impressive double consisting of near-identical white stars, easily separated when viewed through asmall telescope.

\

TINY TRIANGULUM \

To the north of Aries is the smaller constellation of

t h e r a m fl e w t o C o l c h i s o n t h e

Triangulum. This is anarrow triangle of three stars, the

shore of the Black Sea. Here,

brightest being only magnitude 3.0. Although these

^r r P h r i x u s

s a c r i fi c e d

the

ram

stars are not particularly interesting, Triangulum

to Zeus. After Phrixus

died, the Greek hero

.V

Jason and his Argonauts ^

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made an epic voyage h

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s

k

to Colchis to retrieve

the ram’s priceless fleece. Triangulum simply reminded the Greeks of

atriangle.

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contains an important spiral galaxy called M33, the third-largest member of our Local Group. M33 is relatively close to us, at 2.7 million light years away, but

Iit is not too prominent. Aclear, dark night is needed to be able to pick it out using binoculars. It appears as a

a

A ' W

hazy patch of similar size to the full Moon.

Photographs and CCD images show the spiral arms of M33, but visual observers need large telescopes to see them.

.''S

' Va r i e s a n d ries and Triangulum lie highest in the evening sky in November and December each year, between

A

The M33 galaxy, with its pink gas clouds, is Triangulum's claim to fame.

the zodiacal constellations Pisces

and Taurus. They

a r e

visible from all but I

I

the most southerly latitudes on Earth.

IThe Sun passes through Aries from late April to mid May L O C AT I O N

MAP

ABBREVIATION Ari

ABBREVIATION Tri

BEST

BEST

SEASON

SEASON

Late autumn-early winter (evenings)

Late autumn-early winter [evenings]

BRIGHTEST

BRIGHTEST

S TA R

S TA R

Alpha [a] Arietis

Beta ((3) Triangulum

SIZE RANKING 39

SIZE RANKING 78

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"Take ajourney through the Earth’s outer crust to find how churning hot rock is continuously reshaping the surface. "Look outwards to aband of

Constellations that wraps its way around our sky -the zodiac.

"Observe Earth from the European Remote Sensing satellites -ERS-1 and 2-launched in the 1990s.

" U n d e r s t a n d t h e u n i v e r s e a s d e fi n e d

by the 2nd-century astronomer and map-maker Ptolemy. C€

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ISSUE: 47-TOOTH GEAR, EARTH SPINDLE AND EARTH SUPPORT ARM

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SOLAR SYSTEM FEATURES

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3\YOUR SOLAR SYSTEM MODEL See how the zodiac defines our calendar and the measurements we make in the sky.

0 10

SOLAR SYSTEM GUIDE Journey into the churning hot rock deep inside our planet that is continually reshaping the surface.

MISSIONS

I M P O R TA N T "The orrery is aprecision-engineered kit. It must be assembled and handled

with care to prevent damage to Its parts, and stored or displayed safely to ensure no parts are lost. "Never use liquids or solvents to clean

theparts.Forlaestcare,usethe

polishing cloth and dusting brushes supplied with the toolkit (free to subscriptions customers).

"When assembling parts, lay them on a flat table and keep screws and all small items on atray so they can't roll away and get lost. Unpack all parts carefully. "The publisher reserves the right to alter parts and their design at any time.

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"Parts not to be sold separately. "The publisher cannot replace any parts that are damaged or lost by the customer without charge. "The publisher cimnot be responsible for any damage that may occur as a result of incorrect assembly or mishandling of the orrery. Please ensure you read alt the instructions thoroughly when assembling the parts.

"

4

"All tools must be used with care,

following any safety guidelines provided by the manufacturer. "The publisher cannot be responsible for any injuries caused by any tools or

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materials.

Observe Earth through the cameras and sensors on board the European Remote Sensing satellites.

IMAGE GALLERY

12) Spectacular aerial views of Earth's ever-moving tectonic plates in action. 16

2 0

THE STORY OF ASTRONOMY Learn how 2nd-century scholar Ptolemy mapped the world and defined our understanding of the universe.

S TA R M A P Focus your telescope on aplayful dolphin, ahorse's h e a d a n d a c e l e s t i a l a r r o w. m

2 2

#

S PA C E S C I E N C E Find out why only the planets are round, and what pulls heavy metals into planetary cores.

C O N S U LTA N T E D I T O R : G I L E S S PA R R O W E N D O R S E D B Y : S I R PAT R I C K M O O R E C B E F R S E N C O U R A G E D B Y: T H E I N T E R N AT I O N A L A S T R O N O M I C A L U N I O N

CREDITS IMAGES: FC Science Photo

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[1] MOUNT FUJI The

[2] MOUNT ETNA

[3] CALIFORNIA FAULT

[ 5 ] B O G D A M O U N TA I N S

snow-capped peak of the

After an eruption of this

California's San Andreas

One of the few places

sacred dormant volcano

active volcano in Sicily,

fault is the sliding boundary

on Earth where land

pokes through the clouds

Italy, in 1992, ahuge lava

o f t h e P a c i fi c a n d N o r t h

is below sea level, the

above Honshu in Japan. It marks the point where

fl o w t h r e a t e n e d t h e t o w n

American plates.

fault-bounded trough

three tectonic plates

successfully diverted.

[4] HAWAII Asteam

Depression, in north-

meet -the Eurasian (or

For about half amillion

western China, is a

Amurian), the Okhotsk and the Philippine plates.

years, Etna's landscape

plume results from lava sliding into the sea off

h a s b e e n i n fl u x .

the coast of Hawaii.

and sand dunes.

c a l l e d t h e Tu r f a n

of Zafferana, but It was

strange mix of salt lakes

[6] CLEVELAND VOLCANO Stratovolcanoes such as those found in Alaska

a

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steep-sided, multilayered cones built up from repeated

eruptions of lava through the same volcanic vent. The Alaskan volcanoes form part of the enormous Ring of Fire that forms arough circle

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his works on his own

observations of the heavens,

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volume but its breadth. He wrote on the known world. Geographike atreatise on music, Harmonics, hypegesis, or Guide to Geography, explaining how music equated with was acompilation of contemporary mathematics. He investigated the knowledge in which he assigned properties of light in Optics, and in coordinates to all known places, his geometrical work he contributed and created projected maps, to the study of trigonometry with, ASTRONOMY most importantly, atable of chords But it was Ptolemy’s two works on (see Glossary). astronomy that had the most farAs ageographer, Ptolemy reaching effect on world produced the first extensive work knowledge. The first. He Mathematike Syntaxis, or The

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known to Arab astronomers as 'tr^Z^TmiUk tLv A’- -K ^

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"TM. 4. Jf Xi« fr.# /i/ W. J 4 - ' v u s r 4 * S i l t Y * * i

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Megiste, or Great Book. It .acquired its modern title when given the prefix

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Itreatise on iGreco-Roman

Alexandria. Being wealthy and

,1astronomy to

cosmopolitan city, and with the largest library-museum in the world, Ptolemy had the texts of all the major Greek astronomers

^tsurvive into /modern times, rIt provides an encyclopedic

at his disposal, in addition to the writings of his predecessors and contemporaries. While he drew heavily on the studies of those who had gone before, Ptolemy’s body of work is

impressive, not just in terms of its

synthesis of the astronomical knowledge of the ancient world, UNIVERSE

Ptolemy's model was geocentric.

interpreted and substantially supported with rigorous proofs by t h e a u t h o r. 17

CCWHENISEARCHOUTTHEMASSED WHEELINGCIRCLESOFTHESTARS,MYFEET NO LONGER TOUCH THE EARTH.” Ptoiemy

The work is divided into 13 books. The first book outlines the

geocentric system. The second contains atable of chords and

spherical trigonometry. Subsequent books explain the Sun’s motion and

year length; the Moon’s motion, distance and month length; eclipses, conjunctions and oppositions,

THE OLD WORLD

precession, astar catalogue and the

This medieval

movement of the planets.

map of the continents

In addition, there are details for the construction of an astrolabe and

surrounding the Mediterranean was constructed

acelestial globe.

I

j

from the instructions in

C O N S T E L L AT I O N S

He credited his predecessor Hipparchus for much of his solar and

Ptolemy's Guide to Geography.

I, 3

lunar theory, and the star catalogue, which Ptolemy expanded from 850 h

to 1022, and divided into 48

\i S

V

constellations.

His second -later -astronomical

BREAKTHROUGHS

^PTOLEMY’S ERROR

In order to reconcile the apparent of the planets with his desire motion for an Earth-centred system in which objects only moved in amended inherited significant

"perfect” circles, Ptolemy the geocentric model he had from Hipparchus. Most was the equant point -Earth

equant offset an equal amount in the opposite direction. The equant acted as a point around which the deferent circle

rotated with apparently uniform speed. But when applying his own system to the motion of the Sun ~he ignored the equant

was offset from the centre of each

system (left) and used asimpler model (right), which meant that his calculations

'deferent” circle to one side, with the

of the Sun’s position could drift badly.

Earth

Earth

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distance e Centre

treatise appeared in two books entitled Hypothesis ton planomenon, or Planetary Hypothesis, and sets out his

cosmological view. The spherical, stationary Earth, Ptolemy argued, lay at the centre of the cosmos as afixed mathematical point, with the celestial realm, in the form of a

series of spheres, moving around it. This geocentric view later became known as the Ptolemaic system. While it was fundamentally wrong, Ptolemy had no reason -given the knowledge of the time -to suppose it so. His elegant mathematical solutions to the movement of

distance e

the celestial bodies included the

S u n

introduction of the equant (see The deferent and epicycle in the Story of Astronomy, Issue 8). It has been argued -notably by the 20th-century astronomer Carl

Ptolemy’s Tetrabiblos, Four orBooks is one of the first complete

O

manuals of astrology ever written. Considered “at the

-


scrupulously careful to reject any kind of

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superstition, magic, and the interpretation of

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charts to determine a course of action.

PTOLEMY’S ZODIAC An

0

820ao iiiustratton of the Sui

his chariot and the signs of the zodiac from Ptolemy’s Tetrabmios -. still the basic text for astrology.

L G L O S S A R Y

Chord: Astraight line, connecting two points on acurve that, in early trigonometry, was an essential

startingpointformanycalculations.^

LONG-LASTING

This 15th century illustration marks

the longevity of Ptolemy's universe.

Sagan -that Ptolemy’s expertly explained cosmology “helped prevent the advance of astronomy for amillennium.” Certainly his mathematics offered “proof” of

asystem that was fundamentally wrong, but there were few scholars in the following centuries who had the will or freedom to challenge it. HONOURED

The turbulent times following the fall of the Roman Empire in the 5th

century were not conducive to scientific study. War, plague,

disruption of trade and the power of the Christian church put an end

to the quest for knowledge so valued in the ancient world, and

Ptolemy’s works were preserved for several centuries thanks only to the efforts of Arabic scholars.

Yet, in spite of those who have

sought to discredit him, Ptolemy is honoured in astronomy today with two craters that bear his name -one on Mars and one on the Moon -and an asteroid called 4001 Ptolemaeus.

DELPHINUS, EQUULEUS and SAGITTA Aplayful dolphin leaps high in the northern sky. This is Delphinus, and on either side lie Equuleus the foal and Sagitta the arrow.

DOlS^IN W

hen thieves attacked the Greek poet and musician Arion during his return voyage from aconcert tour of the

Greek islands, he was forced to jump overboard to escape the raiders. He was saved from drowning by adolphin, which swam to Greece with Arion on its back. In gratitude, Apollo,

he constellation Delphinus is asmall but

attractive grouping of stars with adistinctive shape, rather like achild’s kite with atail.

Gamma (y) Delphini, at the northernmost tip of the kite, is abeautiful double consisting of orange and yellow stars. They are divisible when seen with asmall telescope. In the same telescopic field of view can be seen another, fainter, double called Struve 2725.

Historically, the constellation was known as

the god of music and poetry, placed the dolphin in the sky. An alternative Greek myth says that Delphinus represents the dolphin that brought the sea nymph Amphitrite to marry the sea-god Poseidon. At least three different Greek legends are associated with Sagitta This celestial arrow was said to have been

shot by Apollo, Hercules, or

Eros, the god of love.

Job’s Coffin, although who named it and when is not known. Presumably the name arose from the perimeter of the constellation, which is distinctly box-like. The name has also been applied solely to the diamond formed by the four brightest stars. Alpha (a) and Beta (P) Delphini bear two of the oddest star names in the sky: Sualocin and Rotanev. Read backwards, they spell out the name Nicolaus

19th-century Italian astronomer who was the assistant

(and eventual successor) to Giuseppe Piazzi at Palermo Observatory. Opinions differ as to whether Cacciatore named the stars after himself or whether it was done

Venator, the Latinized version of Niccolo Cacciatore, a

by the director, Piazzi. GAMMA DELPHINI

SPEEDING ARROW

This double star

Sagitta, in the Milky Way next to Delphinus, consists

can be seen with asmall

telescope. Both are normally described as

yellow but you

m

m

may view the fainter star with abluish hue.

of athin triangle of stars resembling an arrow. It is the third-smallest constellation in the entire sky. Its main feature of interest is M71, amodest globular cluster visible through binoculars and small telescopes as a misty patch of faint light 13,000 light years distant. Between Delphinus and Pegasus lies Equuleus, the

second-smallest constellation, representing the head of asmall horse. The Greek astronomer Ptolemy is said to have invented Equuleus in the 2nd century ad, perhaps as afoal for the winged horse Pegasus. Equuleus’ most interesting object is Gamma (y) Equulei, awide double star of 5th and 6th magnitude that can be separated when viewing with binoculars.

CYGNUS

NGC

6905

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^ S A G I T TA

DELPHINUS IC

4997

PEGASUS NGC !7006

RotanevP \ NGC 6S9'I

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/ NGC

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6934

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P a

Kitatpha EQUULEUS

iIZl A9Ip byIarjcl uste rJn^

itta

some 13,000 light years from Earth.

^DELPHINUS, EQUULEUS AND SAGITTA #

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elphinus and its neighbours Sagitta and Equuleus are best seen in the evening sky in August and September. They lie

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planet we can treat all of this

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if there is somewhere to go. The

higher the force of gravity, the

H Y P E R I O N

Saturn's moon is

it unless something gets in the way or

fragment of a much larger, spherical body that was broken

up, for example, by acollision.

holds it back.

The bigger something is, the

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moon (left) are spherical due to i '

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BREAKTHROUGHS

DWARF

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results in steep¬ sided craters.

be spherical but is highly irregular, suggesting that it might be a

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object on the surface experiences amore-

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the inward pull of gravity, especially

large enough to

towards the centre of

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harder it is to support itself against

Low gravity on

This means that every

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C R AT E R S

differentiation.

PLANETS

he ability to form atruly spherical surface is one of the crucial factors that astronomers

use to decide whether asmall solar system body, such as an asteroid or Kuiper Belt Object, is worthy of the title “dwarf planet”. At the moment, there are three agreed dwarf planets -Ceres (the largest asteroid), and the Kuiper Belt worlds Pluto and Eris.

CO T 3

greater this effect, so the Moon can support deep, steep-sided craters

IIMSIDE INFO

P L A N E TA R Y P O W E R P L A N T S

whose walls would soon slump

In the liquid interiors of giant planets such as Jupiter, Saturn,

Uranus and Neptune, the differentiation process can continue more easily, and it seems that in three of these planets, at least, it’s still going on. Denser material is continuously sinking towards the centre, pushing past lighter material and generating heat through friction as it goes. This kind of heating by gravitational contraction is thought to explain why Jupiter, Saturn and Neptune all emit more energy than they receive from

SIZE MATTERS G L O S S A R Y

As aresult, the greater the size of a

Centre

solid world, the more likely it is to

This is essentially

Because the rocks and ice that

formed early planets and moons had to be melted or at least

crushed and squeezed into place in

of

mass:

the centre of

gravity of abody. In aspherical object such as a

the Sun. Uranus is the only exception to the rule -perhaps as aresult of whatever cosmic catastrophe knocked it over so it now orbits on its side. It’s also worth noting that, although the heating mechanism

planet, it would be expected to be close to the c e n t r e .

order to form such aneat sphere.

is called contraction,

materials

outermost

image shows the excess of energy being generated in the interior of this

gaseous giant.

L same strength on materials of all kinds, denser ones will tend to

sink through lighter surroundings, until the planet’s interior is divided into asequence of layers of widely d i ff e r e n t d e n s i t i e s .

light crust

the size of truly spherical worlds. If they were any smaller, the collisions

G R AV I T Y Differentiation

separates the materials of the

that formed the world in the first

molten interior

place would never get hot enough

(A), to create a structure such

to melt the interior.

Meanwhile, gravity continues to affect the inside of the planet.

Just as outside, it’s possible to keep considering each layer to be pulled towards the centre by the gravity of all the material closer in. Although gravity pulls with the

as Earth today (B). At the same time, it flattens out the surface. V E S TA T h i s distant asteroid is differentiated

despite its small size.

o m

D

Z

JUPITER This infrared

c o r e

Z

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cloudtops.

materials

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on the height of

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so there’s no effect

the

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the planet’s overall mass and gravity are remaining constant,

light

there tends to be alower limit to

O m

inwards on Earth.

have afairly flat, spherical surface.

>

Temperatures also rise closer to the planet scentre as material is packed ever more tightly by the downward pressure from above, and inside the larger solid worlds it can grow hot enough to melt the heavier metals that gather near

T E M P E R AT U R E

the core. As heat rises from the

Iron and nickel, the heaviest common elements in the universe,

core, it creates huge convection cells through the mantle, so

will tend to end up near the centre, where they form adense core.

the separation into layers never becomes complete.

COMING

ISSUE ♦

S E L F - TA P P I N G G R U B SCREWS SCREW

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AMODEL 22-TOOTH GEAR J

SYSTEM

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^precision engineered ORRERY

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of the

moon The ba*rren and

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MARS GEAR ARM

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GEAR AXLE 2’

"Explore the surface of our Moon a n d fi n d o u t h o w i t h a s e v o l v e d

through bombardments from space and global lava eruptions. "The Apollo programe to land on the Moon -one of the greatest achievements in human history. "Moonwatching from Earth with details of visible craters, mountains and “seas”.

From fantasy to fact -how the only ’ body close enough to Earth to be perceived as another world has us

fascinated us throughout history. C€

Eagiemoss Publications Ltd, Beaumont House, Avonmore Road, London W14 STS

WARNING! Accessible gears and small parts. Keep out of reach of children. Keep this Information for reference. Applies to all issues of 'Build AModel Solar System'.

P

(N) An Eaglemoss Publication -Every Week UK £5.99 Malta €8.99 Australia $14.95

BUILD AMODEL

SOLAR SYSTEM ^

[r

1l)

APRECISION-ENGINEERED ORRERY

zxplore the surface

MOON

of the

r

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heavily cratered

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natural satellite

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SOLAR SYSTEM -P

FEATURES YOUR SOLAR SYSTEM 33

♦The orrery is aprecision-engineered kit. It must be assembled and handled

MODEL

Add the Earth-Moon system, completing the second phase of Stage 2of your model assembly.

0

SOLAR SYSTEM GUIDE Explore the highlands, "seas" and craters that dominate the barren surface of the Moon.

1^

■■

I M P O R TA N T

MISSIONS

with care to prevent damage to its parts, and stored or displayed safely to ensure no parts are lost. "Never use liquids or solvents to clean the parts. For best care, use the polishing cloth and dusting brushes supplied with the toolkit (free to subscriptions customers). "When assembling parts, lay them on a flat table and keep screws and all small items on atray so they can't roll away and get lost. Unpack all parts carefully. "The publisher reserves the right to alter parts and their design at any time.

I

"Parts not to be sold separately. "The publisher cannot replace any parts that are damaged or lost by the customer without charge. "The publisher cannot be responsible for any damage that may occur as a result of incorrect assembly or mishandling of the orrery. Please ensure you read all the instructions thoroughly when assembling the parts.

t

"Alt tools must be used with care,

following any safety guidelines provided by the manufacturer. "The publisher cannot be responsible for any injuries caused by any tools or

NASA's phenomenal Apollo programme to put aman on the Moon and win the superpower space race.

IMAGE GALLERY Spectacular pictures taken by Apollo astronauts walking and driving on our desolate Moon. 16

THE STORY OF ASTRONOMY From fantasy to fact -how the Moon has fascinated mankind throughout recorded history.

S TA R M A P Close enough to see some of its features with the naked eye, the great silver orb dominates the sky.

UNEXPLAINED Strange glows reportedly seen on the lunar surface suggest to some that our satellite may not be dead.

CREDITS

■■ I I

I

I

C O N S U LTA N T E D I T O R : G I L E S S PA R R O W E N D O R S E D B Y: S I R PAT R I C K M O O R E C B E F R S E N C O U R A G E D B Y: T H E I N T E R N AT I O N A L A S T R O N O M I C A L U N I O N

IMAGES: FC NASA/Human Space Flight; 2-3 Hubble Heritage Team/ NASA/ESA, (r) Eaglemoss/Simon Anning; 4(t) Rich Richins, (b) Pikaia Imaging, 5(cr) iStpockphoto, (bl) Ceri Loxley; 6-7(tc) NASA/JPL, (be) NASA/Human Space Flight, (tr) Pikaia Imaging; 8-9{cl) NASA/JSC, (tr) NASA/Human Space Flight, (cr) NAS/VJPL, (b) Pikaia Imaging; 10-11 NASA/Human Space FlighVMSFC/ JSC; 12-13 NASA/Human Space Flight/JSC; 14-15 www.moonpans. com; 16 Mary Evans Picture Library; 17(tr) Science Photo Library/Royal Astronomical Society, (b) University of Liverpool; 18(t) Rex Features/

Everett Collection, (br) Science Photo Library/Detlev van Ravenswaay; 19(t) Rex Features/ SNAP, (c.bl) Mary Evans Picture

Library; 20{bf> Pikaia Imaging, (br) Galaxy Picture Library/Jamie Cooper; 21 NASA/JPL; 22{tl) Leon Stuart/Department of Astronomy, Columbia University, (bl) Jean Pierre Martin; 23{t) Pikaia Imaging, (b) NASA/Human Space Flight. REPRO; Stormcreative

Publishing Limited

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PRINTING: Century Litho (Truro) Limited

Eaglemoss Publications Ltd,

BeaumonlPHouse, Avonmore Road, Lon^|Bii^W14 STS WARNING! Accessible gears and small parts. Keep out of reach of children. Keep this information for reference. Applies to all issues of 'Build AModel Solar System'.

©Eaglemoss Publications (2008). All rights reserve^. ■ 1

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. /ou have now collected all tife components to build the second phase of Stage 2of your solar system model. The instructions for constructing

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^to make Earth rotate as it orbits the Sun. The gear ratios

I’:, are calculated tcrrepresent btth these interconnected sets iof motions accurately, fei. When all the Stage 2phases are completed (there are

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unit to fit into abase unit This motor can be calibrated so h:

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LUNAR T H E M O O N ' S PAT H Astronomer Rich Richins

photographed the Moon over amonth in New

Mexico, USA, then montaged the images on his computer.

MOTIONS

The Moon is acomplex object

to track through Earth's skies -governed by its own motion and the Earth's orbit around G L O S S A R Y

Celestial equator; The line separating the sky's own northern and southern hemispheres.

the Sun, it repeats its cycle just once every 18.6 years.

he main pattern of the Moon around the sky is obvious to everyone, and easy to track. As it orbits the Earth every 27.3 days,

the Moon moves farther and farther to the east of the Sun. It rises and sets about 50 minutes later

every day until eventually it completes its circuit and approaches the Sun again from the west. With each orbit of the Moon, the Sun has

itself tracked some way farther along its annual path through the sky, so the Moon has to move

A

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orbit of Earth ...

plane of ecliptic Line of Nodes

5.2 degrees

3

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when afull or new Moon coincides with one of the nodes.

orbit of Earth

plane of ecliptic Line

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through the Earth. Eclipses can only happen ^

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he Moon sorbit (Aj is tilted at an angle 5.2 degrees from the plane of the ecliptic -the apparent path of the Sun around the Earth. The two points where it crosses the ecliptic, known as “nodes”, are joined by the so-called Line of Nodes passing

T of

of

Nodes

The Moon’s entire orbit spins slowly around the Earth, completing one circuit every 18.6 years (B]. As aresult, the orientation of the Line of Nodes changes direction, and the opportunities for eclipses tend to follow arepeating cycle.

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7 ^ CO FUTURE MOON BASES

Space explorers may eventually be

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based on the Moon -as depicted in this Pat Rawlings painting.

BREAKTHROUGHS

^THE SOUTH POLE-AITKEN BASIN

T

he largest crater known in the solar system lurks at the Moon’s south pole. The South Pole-Aitken basin, 2500km across, was

u n d e t e c t e d u n t i l t h e 1 9 6 0 s ( a n d n o t c o n fi r m e d u n t i l t h e

1990s] because it lies mostly on the far side of the Moon, and never filled up with basalt lava to form alunar mare. The object that formed this crater 3.8 billion years ago

L AVA F L O O D S

O

Soon after the Late Heavy Bombardment v o l c a n i c eruptions engulfed the Moon. They were triggered as its internal temperature peaked, due to heat caused by the tidal pull of the Earth and the decay

a

of radioactive elements in the mantle. Tidal forces

helped volcanic magma reach the surface on the

Moon’s Earth-facing side, and so basalt-rich lavas flooded out to fill up the impact basins here. As the lava cooled and

must have been more than 100km

across. Although the crater is up to 12km deep, it must have formed in a collision that occurred at quite low speed -otherwise such ahuge impact

s o l i d i fi e d v o l c a n i c

activity on the Moon mslowed to ahalt, and its evolution essentially came to its end In the 3billion or more years since the last seas formed, impact craters have continued to reshape the surface Most are microscopic and do little but

would have excavated material from the mantle.

The basin is filled and deepened by many later craters, and some of these. lying close to the south pole, have rims that are in constant daylight and floors In permanent shadow. This combination, with unceasing solar power and potential hidden deposits of ice. makes the lunar south pole alikely l o c a t i o n t o b u i l d t h e fi r s t m o o n b a s e .

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BIG BANG

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grind the regolith into ever-finer dust, but the occasional larger impact hollows out ahuge impact crater and may fling bright

rays of dust far across the lunar landscape.

This huge crater is the largest in our solar system.

M O LT E N L AVA C O O L E D t o f o r m

eruptions flooded the impact

the lunar maria seen today. Crater formation continues to this day but at

basins on the near side.

amuch reduced rate.

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0 11 O d V S V S V N

IIMSIDE lIMFO

THE TRAGEDY OF APOLLO 1

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n27 January 1967, the three crew members that would have flown on Apollo 1Virgil ‘Gus’ Grissom. Ed White and Roger BChaffee »were testing the command module for ascheduled launch on 21 February, Some five hours into the test, asudden voltage change was recorded and 10 seconds later the crew urgently reported afire. Within 17 seconds the cabin exploded. It took five minutes to open >

the hatch and as the smoke cleared it was

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evident that the three men were dead. ;

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Extensive changes were made as a result, the most significant being that the cabin atmosphere at launch became sea-level pressure air rather than high-

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pressure pure oxygen in which abar of aluminium can burn like wood.

’Tof thrust and burned for just a Jrom

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150 seconds, to accelerate the |

spacecraft to about 9000km/h. | ol- jAgreat deal of trial and error vs^ent

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into ensuring that the combustion remained stable. The second

;^Sta^ consist of five 1^2 engihes.' "

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three astronauts from launch and-b^.,, ft v\^felativety1ight^g^ ;

aof 24,000i^/h:any erh

to splashdown. It included adocking ^il^£a|^tte^landir^ onifee Moon,

altitude of about 185km.

tunnel through which the astronauts could transfer to the service module

(SM). The SM housed arocket engine, fuel, oxygen and water. The lunar module (LM) consisted of two stages -adescent stage and an ascent stage. The descent stage had enough storage for both lunar

would not have been able to fly in Earth gravity. By the end of the decade, Apollos

■The third stage, with asing engine, put the vehicle into orbit and was designed to be restarted in order to perform the translunar injection burn (see Glossary), The command module (CM) was

surface science instruments and a

Ifconicalinshapeanddesignedtocarrylunarrover(fromApollo15onwards), THE FLAG Commander

John Young

jumps beside the Apollo 16 lander. The US flag w a s supported by a metal arm.

RECOVERY

The Apollo 11 command module is winched aboard the USS Hornet after

splashdown in t h e P a c i fi c O c e a n

24 July 1969.

7and 9had flown into Earth orbit,

and Apollos 8and ID had flown into lunar orbit. Launched on 16 July 1969, Apollo 11 landed the lunar module on the Sea of Tranquillity, just over six hours later, Neil Armstrong stepped on to the Moon's surface.

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[6] LUNAR LANDSCAPE This composite photograph, taken by Apollo 17 commander Eugene Cernan, captures the magnificent desolation of the Moon as fellow module pilot Harrison Schmitt lopes across the barren surface towards the lunar Rover. During three such Moonwalks

MOON: r r o m

As anear constant presence in Earth's skies, and the only object close enough for us to

perceive as another world, the Moon has fascinated mankind throughout history.

M

ankind must have been

should have ended our reliance on

aware of the Moon

it, but the Moon still had auseful

long before our ancestors developed the technology

role to perform in splitting up the

to build astronomical monuments,

the seasons. Above all, though, the

let alone to write.

Moon became symbolic.

The cycle of bright and dark

erected monuments that recorded

would have affected the way our

the pattern of its motions and storytellers associated the ever¬ present, ever-changing Moon with

Among his many

when, for example, it was safe to move at night, and when it was

tales, the 17th-

better to remain huddled around

century Baron

the fire for protection. The move into permanent settlements and towards agriculture

Munchausen claimed to have been to the Moon.

Bronze-age megalith builders

nights throughout each month hunter-gatherer ancestors lived TA L L S T O R Y

calendar and helping to measure

various deities -usually goddesses,

inspired by the link between the lunar cycle of phases and the female menstrual cycle. FOLK TALES

The obvious markings on the Moon inspired speculation and folk tales

BREAKTHROUGHS

7THE FIRST MOON MAP

T

he earliest known image of the Moon lies hidden at the heart of a

5000-year-old burial mound in Ireland’s County Meath. The mound of Knowth is ahuge dome of earth, enclosed with slabs of stone. At its h e a r t i s a s m a l l c h a m b e r, w h e r e s u n

or moonlight can only penetrate for a short time on afew days of the year. In 1999, Canadian space scientist

from the earliest times (see Philip Stooke, sifting through manuscripts and photographs in search of ancient maps of the Moon, recognised that aseries of arcs and circles carved into stone slabs in the

central chamber bore astriking resemblance to the lunar maria. Today this is widely accepted as an early map of the Moon, probably made for use In some kind of ritual.

Breakthroughs). Different cultures tended to see different patterns

among the dark blotches of the maria (see Glossary). Most common was a“man in the moon” -usually

depicted as ahuge grinning face but Chinese observers believed they saw ahare, and the Maoris of New Zealand thought there was awoman in the Moon.

X

JOHANNES HEVELIUS (i6ii-i687)

m CO

Polish astronomer Johannes trained as alawyer travelled around Europe before settling Hevelius back in his home city of and Gdansk in 1639.

I

o

There he built himself alarge private observatory with patronage from King Jan III Sobieski. Despite his mistaken interpretation of lunar features, his Moon map was the most accurate of its time, and he carried this accuracy

7 0


CO PO

o

end result was less accurate

than it should have been,

thanks in part to Hevelius’s stubborn refusal to adopt the latest observing methods.

O

0

MOON MAP Hevelius’s map of the Moon (left). Apicture of the 17thcentury Polish astronomer (right), the founder of lunar topography, and his wife, carrying out his work from his observatory in Danzig (now Gdansk), Germany.

Some Muslims even believe

Ali, successor to the prophet

Assyrian-born, Greek-educated Lucian tells of agroup of travellers who are swept up to the Moon on

Mohammed, can be seen written in

agiant waterspout as they travel

t h e M o o n ’s m a r i a .

through the Strait of Gibraltar. Here

that the name of the Imam

they find themselves caught up in

But when was the Moon first

recognised as aworld in its own right? It’s hard to tell for certain, but

aconflict between the King of the

in the 5th century bc the philosopher

the rights to Jupiter.

Moon and the King of the Sun over

MYSTERY ii CREATESWONDERANDWONDERISTHE BASIS OF MAN’S DESIRE TO ONDERSTAND.

93

Neil Armstrong

Anaxagoras was already speculating

ALIEN LIFE

about life on the Moon.

Lucian’s Moon is populated by a variety of unlikely inhabitants including flea archers and cloud centaurs. His story was intended more as atwisted parody of far¬

And when Aristarchus first estimated the relative distances of

/ ^ L U C I A N This Greek writer

penned one of

^the first stories -

^of man travelling ^to the Moon on awaterspout.

the Moon and Sun in the 3rd century BC, he was certainly working from an assumption that the Moon was a spherical body not unlike our own. The best known early speculation

fetched travellers’ tales and the

on the nature of the Moon comes

nevertheless, the first known

from Lucian of Samosata, asatirist

discussion of extraterrestrial life,

of the 2nd century ad. In his ironically titled ATrue Story, the

and the first work to treat the Sun,

foibles of his own society than as a serious essay on the Moon. It is,

Moon and planets as objects similar

by ahelpful daemon. Apart from that, though, Kepler demonstrated aremarkable foresight into the practicalities of alunar voyage.

The travellers depart, for example, during alunar eclipse in order to shield themselves from harsh

sunlight beyond Earth’s atmosphere. They have to endure powerful accelerations during “lift off’’, and they even travel along aspiral flightpath in order to take account of the Moon’s

own motion along its orbit. Once on the Moon, Kepler uses

the trip as an excuse to explore the practicalities of lunar day and night -he recognises that each “day’’ lasts an entire month, and that one

to Earth and worthy of exploration. Lucian even describes Earth hanging in the lunar sky in away that

prefigures the famous Earthrise images from the 20th-century Apollo spaceflights. After Lucian, there was along gap

before anyone considered the Moon as asubstantial world again. The rise of Christianity enshrined agreat many ideas from Greek philosophy, and included among these was Aristotle’s belief that the Moon,

KEPLAR^S DREAM

Inspired by his reading of Lucian’s work, and by the ongoing debate about the shape of the Solar System, German astronomer Johannes Kepler

SILENT MOVIE The classic

image from the Georges Melies 1902 film ATr/p to the Moon.

made the next significant contribution

to bolster the case for aSun-centred,

to understanding the Moon. His book, Somnium {Dream), was

rather than an Earth-centred, universe.

Others soon followed -the Bishops of

published posthumously in 1634 but was actually written around the time

G L O S S A R Y

of Galileo’s observations.

Maria:

Kepler begins with his hero, Duracotus, transported to the Moon

side of the Moon faces permanently away from Earth. The Moon itself is depicted as aworld of exaggerated geography, and gigantic plants and animals -recognising the effects that weaker gravity might have on aworld. Kepler’s main intention was

The

l a s

(singular Mare] on the Moon.

Hereford and Chester both published works on the subject in the mid1600s, with asimilar mix of surreal

fantasy and scientific prediction, while

Sun and planets were perfect, unchanging spheres. INSIDE INFO

m s

GALILEO'S REVOLUTION In late November 1609, that all

1647, InJohannes Polish astronomer Hevelius (see Space

changed. Italian astronomer Galileo Galilei turned his primitive telescope

Stars on page 17) published Selenographia, ameticulously

towards the Moon for the first time

drawn atlas of the Moon. But

and what he saw revolutionised

despite developments in telescopes at the time, he nevertheless sprinkled his map liberally with oceans, and peopled

astronomy. The Moon was not, as

1500 years of Church dogma had insisted, aperfect ball. The long shadows along the terminator between night and day revealed the presence of mountains, valleys, and

it with Moon-men or Selenites.

Just four years later, however, Giovanni Battista Riccioli

published his own lunar map (coining many of the names of

countless craters. The following year, Galileo publicised this and his other telescopic discoveries in his book.

maria and craters still in use

today) and he was equally insistent that our satellite was a

The Starry Messenger. Once again, people began to consider the Moon as areal world.

%

barren, airless ball of rock.

L

RICCIOLI’S MAP The 1651 map that has stood the test of time.

opinions began to change. But the

SCI-FI

“life” debate rumbled on for

MOONSHOT!

another century or more, although

erman film director Fritz Lang based his 1929 film Frau im Mond [Woman on the Moon] on the latest research into spaceflight, hiring rocket scientist

Hermann Oberth as consultant. Although the film accurately depicted the effects of space travel, and showed the

ich improvement in pe power and each new

ie case against life on the One “last hurrah” for

showed the space travellers walking around on the lunar surface without

expectations of lunar

protective spacesuits. Its main claim to fame, though, is the invention of the countdown -added to the launch by Lang in order to build tension. The lasting influence is all the more surprising considering that Frau im

life came, nevertheless,

I

in 1835, when US

journalist Richard

The 1929 movie by Fritz Lang introduced the idea of arocket launch countdown.

was probably satirical rather than

the great writer's

1901 novel, The First Men

1865 book,

in the Moon.

to the Moon.

intentionally misleading, but a

fascinated public convinced itself that the reports were true, and eagerly awaited each new report.

From the Earth

> LO

I

O

the Cape of Good Hope. Locke’s intention

The cover of

O

of articles for the New

strange alien creatures supposedly made by Sir John Herschel from

WOMAN ON THE MOON

in HG Wells'

7 3

73

on obser v a t i o n s o f

Moon creatures

O

Locke wrote aseries

York Sun, reporting

Mond was asilent movie.

JULES VERNE

m

Moon became stronger.

Moon as abarren wasteland, it also

SELENITES The

X

O

0 X m

o o

In the aftermath of this

embarrassment, no one took

T l

the idea of life on the Moon

o

seriously again, although the Moon continued to be arich topic for the

growing genre of science fiction. In 1870, French author Jules

> >

Verne wrote of atrip Around the Moon in aprojectile fired from

t

an enormous cannon, while a

o

generation later, HG Wells wrote of an encounter with insect-like,

cave-dwelling Selenites ruled over

o

-
o H

by an enormous brain known as the Grand Lunar. However, Wells’

First Men in the Moon (1901) was intended as acommentary on the French poet Cyrano de Bergerac wrote awilder fantasy that hit upon the idea of rockets for space travel.

human society rather than aserious speculation about lunar civilisation. Throughout the 20th century,

T H E G R E AT D E B AT E

the Moon became asubject for serious debates about its origin

All these works took it for granted

and the nature of its surface, but

that the Moon could be an

even in the age of the Apollo Moon missions, it would never again

inhabited world, but as telescopes

improved and the true nature of the become the strange, romantic 1

r

lunar landscape became clear.

otherworld of earlier times. 19

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9 N I H 3 1 VA \ N O O W

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labelled with

^THE MOON sit orbits the Earth the Moon goes acycle of phases, due to the ;fact that we see differing proportions

A through

:of its sunlit side. When the Moon is a

%

V

young crescent it will be found low down

Iin the evening twilight after sunset. IThereafter it moves away from the Sun, Irising about 50 minutes later each night. IThe phase increases, first to half (when

NEARSIDE

The seas are C A P I TA L S a n d

the Moon lies 90 degrees from the Sun], then via what is termed the gibbous phase, until eventually we see the Moon fully illuminated. When full, the Moon lies opposite in the sky from the Sun and rises as the Sun sets. It then goes through the cycle In reverse, ending up between us and

lunar landing sites are labelled with italics.

the Sun, when it is invisible.

21

TRANSIENT PHENOMENA Is our satellite the dead world that it appears to be? , Ta H : 1 m'-

^Perhaps not, according to the many amateur and professional astronomers who have witnessed

1^^ strange glows on its surface.

''

.^3

A

Ithough geological activity on

been the most spectacular. In June 1178, agroup

billions of years ago,

of monks from Canterbury, England reported that

astronomers have long been vexed by reports of strange glows of light on the lunar surface. These short-lived outbursts

usually disappear before witnesses can contact other observers for confirmation, and for a LUNAR FLASH ThisTLP

flash (centre), recorded by

long time they were considered little more than tricks of the light or observing errors. But today

astronomer Leon Stuart on

most scientists admit there is something going on

15 November 1953, has

-even if they don't understand the cause. For that reason, they have given these strange, ephemeral glows the non-commita! name of transient lunar phenomena (TLPs for short).

been linked to ahouse¬ sized crater revealed in

images taken by the Clementine orbiter in 1994.

The earliest recorded TIP also seems to have

the Moon came to ahalt

shortly after sunset the crescent Moon seemed t o split in tv\/o”, belching out acolumn of flame several times. Later ones seem to have been

almost as impressive. William Herschel. discoverer of Uranus, believed that he was seeing erupting

volcanoes on the night side of the Moon when he recorded three red spots there in 1787. LACK OF PHOTOS

Later experienced observers such as lunar map-

makerJuliusSchmidtandOttoStruve(famousfor his catalogue of double stars) also recorded unexplained patches of brightness. In our own time, TLPs have been recorded by Patrick Moore and French veteran astronomer Audouin Dollfus (see

SpaceStars).Manyamateurshavealsorecorded them, but there is afrustrating lack of convincing

photographic proof, or simultaneous observations of the same TLP by observers in different places. Perhaps the most convincing observation so

far was made in July 1969, when reports of a TLP close to the crater Aristarchus were rapidly

transmitted to the orbiting crew of Apollo 11, and

Neil Armstrong reported that he thought he could see some kind of brightening in that area. The fleeting appearances of TLPs offer some excuse for the lack of conclusive proof, but the best evidence is statistical. The glows seem to cluster on certain areas of the Moon’s disc in away that they should not if they were entirely random events or misinterpretations of optical i s i o n s . So what might cause the TLPs? The earliest theory, advanced by Herschel, was that they

X A c c o r d i n g to the outgassing model, alarge, relatively

rAyoung crater (A) still has small pockets of gas trapped in the lunar regolith (the blanket of loose soil at the surface). The crater walls and floor may also be unstable.

Shockvtfaves from ameteorite impact (B) cause the walls of the larger crater to slump inwards and the floor to subside, allowing the trapped pockets of gas to escape where they briefly form aTLR

“ D

> m

B

u

h

1 incoming meteorite

meteorite impact

> z gas

CO

escapes

z

m 7trapped gas /pockets

% orator

;sHockuifaves

lunar regoitth

i

t

waif

and

>

fioor coitapse

- D “

were indeed active volcanoes, but the intensive

studies carried out before and during the Apollo programme made it very clear that the Moon is ageologically dead world where even the most

recent lava flows are more than 3billion years old. Another theory is that the glows might be caused by trapped pockets of gas escaping from beneath the surface (see Inside Info). Related to this is the idea that TLPs are caused by dust clouds briefly suspended above the surface -although the Moon has no atmosphere and barely any magnetic field, it seems that moondust

Even though the impacts probably happened SEISMIC TESTS

Equipment left on the

tens of millions of years ago, the surface here might still be unstable, and prone to landslips that could release puffs of dust or pockets of trapped

Moon by Apollo 16 included an experiment to detect moonquakes -and then, possibly, link them

gas (should they exist). The slips themselves might

to occurrences of TLPs.

nearby, or by deep-seated "moonquakes

be triggered by the arrival of asmai

between the Earth and the Moon.

C A N T E R B U RY M Y S T E RY What are we to make of that first

likely that this was an altogether

over the landscape. This creates

more impressive event -the formation of amajor new crater on the Moon. In 1976, geologist Jack BHartung even proposed that they might have witnessed

CLUES IN THE DUST

the creation of the young, 22km

What could trigger these unexpected puffs of gas or dust from the lunar

crater Giordano Bruno, on the

surface? The clustering of TLPs

M o o n ’s d i s c .

around particularly young features

extreme eastern limb of the

However, the fact that no one

on the Moon offers aclue. These are

seems to have witnessed the

areas where the terrain was

subsequent meteor storm that would have followed such alarge impact suggests that Bruno might not be the explanation after all.

reshaped in the (relatively) recent past by impacts from space and the formation of new craters.

>

themselves caused by tidal forces

charge that causes it to hang briefly

southern lights.

z

that are

and most spectacular TIP of all, seen by the monks in 1178? It’s

resemblance to Earth’s northern and

o

meteorite

can sometimes pick up astatic electric

shimmering sheets with apassing

T

23

COMING UP IN ISSUE 12 ®A„E.,

MDA^IoSi

SOLAR

tiiimi J

SYSTEM Aprecisionri/.

!

T i

MARS*

M o o m

9

12)

-engineeredorrery

marT"

Arocky world

o f

.'^spires great '^agination

vertical support a r m

PLANET SUPPORT ARiH

Outermostoftherockyplanete^^

o;.

Mars the War God ~observe the

and the most Earth-iike, Mars has

angry Red Planet as it brings

arugged surface featuring deep canyons, high volcanoes, wind-

Colour to our night sky.

sculpted dunes and plains scoured by dust devils.

C€

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See how the Mariner programme revealed Martian riverbeds, craters and mountains in fascinating detail 12

IMAGE GALLERY

*

Awesome pictures of Valles Marineris, Olympus M o n s , Vi c t o r i a C r a t e r a n d o t h e r M a r t i a n w o n d e r s .

16

THE STORY OF ASTRONOMY Myth or fact? For hundreds of years many scientists believed there could be intelligent life on Mars *

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S TA R M A P Mars, can often be seen with the naked eye from Earth. Find out where to look.

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UNEXPLAINED The Viking missions failed to find life on Mars, but could their tests have actually destroyed evidence?

C O N S U LTA N T E D I T O R : G I L E S S PA R R O W E N D O R S E D B Y : S I R PAT R I C K M O O R E C B E F R S E N C O U R A G E D B Y: T H E I N T E R N AT I O N A L A S T R O N O M I C A L U N I O N "

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Jeremy Horner; 7(d) Alamy/ Worldspec/NASA; 7(br) Pikaia

Mary Evans Picture Library; 18(t) Mary Evans Picture Library; 18(bl) Topfoto/British Library/Hip, 18(br) Topfoto/Topham Picturepoint; 19(bl) Topfoto/Topham Picturepoint; 19(tr) Topfoto/World History Archive; 20(t) NASA/ APOD; 20(b) Pikaia Imaging; 21 (t)

Imaging; 8{tr) Bridgeman Art Library/Trustees of the Watts Gallery; 8(bl) NASA/Landsat 7 Project/APOD; 9{c) Alamy/ NASA/APOD; 21(b) Pikaia Blickwinkel, 9(t) Alamy/Barrie Watts; 9{r) Corbis/Epa/Tannen Imaging; 22(b) Corbis/Jim Sugar; Maury); 10(b) NASA/USGS; 10(tl) 22{t) Science Photo Library/David Science Photo Library/US Airforce; RFrazier, 22(1) Science Photo 11 (tr) NASA/GSFC, 11 (b) Courtesy Library/Professor NRussel; 22Tom Hill/NASA/GSFC/USGS; 11(tl) 23(b) Science Photo Library/ Science Photo Library/NASA; 12 Lynette Cook; 23(br) Science NASA/GSFC; 13(t) NASA/GSFO Photo Library/Sinclair Stammers; Craig Mayhew &Robert Simmon, 23(b) Topfoto.

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NASA/Jeff Schmaltz; 14-15 NASA/

GSFC/Reto Stockli; 16(bl) Topfoto/ Fortean; 16{t) Topfoto/World

REPRO: Stormcreative

History Archive; 17(t) Pikaia

Publishing Limited PRINTING: Century Litho (Truro)

Imaging; 17(cr) akg-images; 17(b)

Limited

Eaglemoss Publications Ltd,

BeaumontHouse,AvonmoreRoad,LondonW14StS^. WARNING! Accessible gears and small parts. Keep out of reach of children. Keep this information for reference. Applies to all isSies of 'Build AModel Solar System'. ©Eaglemoss Publications (2008). All rights reserved.

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orbittheSunonanac^fratelypac^d'pathbeyond

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Earth. Towards the end of the series, in Stage 3, you get avariable-spSed motor unit. This can be

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ITHE RED PLANET * With the parts suppifed

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with issues 12 to 16,

m

you can build the gear

calibrated so that the orbit of Mars around the

train and support arm

Sun takes 68.7 seconds, giving acomparisbf yy/itlt

m #

that carry Mars and its

m

fnoons in orbit beyond

the orrery model of o^e second equal to 10 real Earth days. (Mars takes 687 Earth days to orbit the Sun.) Agrub screw in the gear collar enabft tht e

the Earth.

planet support arm to be slad m r o

Now attach the Mars support arm (05) to the large gear set. Feed the arm into the designated hole on the collar and secure with a grub screw (M3G 5mm). Push the pin of planet Mars through the hole in the collar of

7

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X M A R

CO

CO

0 5

(NOTE: All planet arms have a1 hole in one end only for the planet’s pin, so ensure you fit

the arm with this hole uppermost.) SlH! H0f

m iM'hTiiir

mi M 3 G

m

MMO^

the Mars moons (MMO), then locate the pin at the base of planet Mars with the hole in the top end of the arm. I

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The RED PLANET

MARS Half the size of Earth and covered

in fine rusty sand, the famous Red Planet is deceptive -it's actually the most Earth-like world in our

solar system.

V

ars is the outermost of the rocky planets that dominate the inner solar

system -it is larger than Mercury, but considerably smaller than Earth or Venus. Mars is a

complex world that has been shaped by all the same forces as our own planet. Today the two planets look remarkably different, but in the past Mars was probably much more Earth-like. OUR OUTER NEIGHBOUR

Mars orbits the Sun once every 687 Earth days, at an average distance of nearly 228 million km (142

BROWN PLANET

million miles). Unusually among the major planets,

Despite looking red from Earth, close-ups show

its orbit is noticeably elliptical (stretched), so at one end it comes as close to the Sun as 207 million km,

Mars to be dull brown.

The vast canyon complex

while at the other extreme it is 249 million km

n a m e d Va l l e s M a r i n e r i s i s

away. Only tiny Mercury’s orbit is more elongated.

the predominant feature,

The Martian orbit interacts with Earth’s so that

c e n t r a l i n t h i s v i e w.

the distance between the two worlds is constantly

O

varying. Because of this, close approaches between / PLANET

Mars and Earth, which occur every 26 months or

so,varybetween57millionand99millionkm.The^ closest approaches take place every 16 years. While the Martian year is notably different from Earth’s, the day and pattern of seasons are surprisingly similar -the planet rotates in 24 hours 37 minutes, and is tilted on its axis at 25.2 degrees

PROFILE

MARS

asE

HE lira

lili]

HE H E

1 0.284

Earths

V O L U M E C O M PA R E D TO E A RT H

-125°C to +25^C A X I A L T I LT

0.15 Earths

25.2 degrees

E Q U AT O R I A L S U R FA C E G R AV I T Y

AV E R A G E O R B I TA L V E L O C I T Y

3.75m/s2

24.1km/s

O

ODD

ORBIT

Unlike Earth, Mars has an eccentric orbit that

207 million km (min)

249

O

millii

ranges from 207 to 249 million km from the Sun

>

and brings it as close as

7 0

57 million km to Earth.

CO CO

H r, . .

6 99

million

m

km

o u m

0 from “straight up” -slightly more than Earth’s own 23 degree tilt. This means Mars goes through its own cycle of seasons, as first one hemisphere and then the other is exposed to more sunlight. The seasons can be observed from Earth, since

they are revealed by the growth and shrinkage of the planet’s icy polar caps. These distinctive white spots at the north and south poles of Mars were first noticed by astronomer Christiaan Huygens

around 1659 (see Space Stars on page 9). While

Earth’s caps are made entirely from frozen water, most of the visible ice on Mars is simply carbon dioxide frost, known on Earth as “dry ice”. Carbon dioxide (CO2) is plentiful on Mars

because it is the dominant gas in the planet’s thin atmosphere. It freezes at -79°C and is unusual in that it bypasses liquid form and condenses directly into solid frost. Similarly, it evaporates straight from solid into gas (a process called sublimation). Despite this, the carbon dioxide frost is just athin layer, and the bulk of each polar cap is made of more familiar water ice -either on the surface or

mixed with the soil. The overall extent of the caps

grows and shrinks as carbon dioxide frosts form and evaporate in autumn and spring. ICY POLE

This Viking Oribiter 2 image shows that Mars' South Pole is covered in ice and frozen CO2.

VOLCANOES, CRATERS AND CANYONS From Earth, the surface of Mars appears to be

spotted by avariety of darker regions such as Syrtis Major, Acidalia Planitia, and brighter areas such as Argyre and Hellas Planitia. Until the dawn of the space age, hopes were high that the dark patches might indicate vegetation or other primitive Martian life -Mars was expected to be acomplex world similar to Earth. The first space probe flyby

R U S T Y S U R FA C E

Mars has oxygen -not in the air but locked in the

soil as iron oxide (rust).

D n o

>

> T O L D

S U D D E N I M PA C T

MIGHTY MONS

Mars' Hellas Planitia

Olympus Mons, the

region is ahuge impact basin that was probably caused by astray comet

tallest volcano on Mars, towers 17km above the

Tharsis Plateau (27km above the mean surface).

or asteroid.

(by Mariner 4in July 1965) was something of a disappointment, revealing only aheavily cratered, moon-like landscape.

Despite two more flybys, by Mariners 6and 7, it was afurther six years before perceptions of the planet changed again. Mariner 9was to be the first probe into orbit around Mars, and when it arrived

in November 1971, it found the whole planet engulfed by one of the periodic dust storms that sometimes obscure the surface.

As the atmosphere finally cleared, the probe

began to send back photographs of enormous volcanoes, larger than any on Earth, and ahuge system of canyons, far longer and deeper than

HOW

IT

WORKS

^INSIDE MARS

M

ars formed in afairly similar region of the solar system to the Earth, and so it contains roughly the same mix of

material from the original cloud of gas and dust that orbited the young Sun. As aresult, Mars has asimilar internal composition to Earth, with anickel-iron core and amantle of silicate minerals

underlying arocky crust. The major differences are due to the red planet’s smaller size -this caused Mars to cool down more rapidly, so that its crust never had achance to crack apart into tectonic plates, and its small core became completely solid early in Martian history.

One distinctly unusual feature of Mars is that it is not truly spherical. The Tharsis region, underlying the major volcanoes, forms ahuge bulge rising 10km above the surrounding surface

Earth’s Grand Canyon and soon named the Valles

level. Astronomers are still

Marineris. What was more, there were signs of what appeared to be dried up river beds, and even oislets formed by catastrophic flooding.

unsure whether this “Tharsis

rise’’ has been pushed up by forces inside the planet or is formed from deposits of

COLD AND LIFELESS

volcanic lava that

If Martian history was becoming more complex

I. are layered onto

and interesting, it still looks adry, cold and dead

■' - M i

the crust.

world today. The Viking orbiters and landers of the mid-1970s appeared to confirm this solid

impression when their tests for possible organic matter in the Martian soil gave seemingly negative results (although see Unexplained pages 22-23 for another possible explanation). The Vikings were the last successful missions to Mars for more than adecade -NASA had other

priorities throughout^he 1980s. The old Soviet space agency and its successors made several

valiant attempts at reaching Mars, but these

iron

nickel

Silicate

*

1

rocky crust

core

mantle

and

n

0

rbiting around Mars are two tiny, irregular satellites ~Phobos and Deimos -that went undiscovered until 1877. Close-up photos

from the Viking orbiters and other probes show heavily cratered worlds. They look like refugees from the asteroid belt -and almost certainly are. Knocked out of the main asteroid belt by repeated runins with Jupiter’s powerful gravity, they were later captured by Mars. Phobos and Deimos both orbit much closer to Mars than our

huge deposits of ice mixed in with the soil, and possible signs that water occasionally flows on the surface today. There are more volcanoes than suspected -many on asmaller, Earthly scale -and some may still be active. And there are complex cycles of weather and climate change, plains scoured by whirling dust devils and deserts full of bizarre, wind-sculpted dunes. In the next few issues, we look at many of these newly discovered

7hours

and 39

orbits mins.

18

mins.

Most enticing of all, there is the possibility of life on Mars. Despite all our

So

discoveries, the Martian environment is

even though they are only 27km and 15km long respectively, each is easily distinguished in the

still hostile, with athin atmosphere

dominated by carbon dioxide and no ozone layer or strong magnetic field to

Martian skies. The Mars

shield the surface from fierce solar

Exploration Rovers, Spirit and Opportunity, even photographed the two moons as they crossed the Sun during partial eclipses.

radiation and high-speed particles from

Phobos’s orbit is so close

be more Earth-like, so discoveries on

the Sun. But at least it is not the arid

to Mars that it is unstable,

losing alittle height each time. In about 50 million

years, its orbit will send it plunging down onto the surface of Mars itself.

CO

-< CO m

POSSIBILITY OF LIFE

23,500km and orbits in hours

>

O

in

Deimos

lies much farther out at

30

O

wonders in more detail.

Moon does to Earth. Phobos has an average distance of just 9380km

CO

end, losing contact shortly after reaching orbit. BACK IN THE SPOTLIGHT

It was not until 1997 that exploration of Mars resumed in earnest. On 4July, the lander Mars

Pathfinder parachuted onto the surface, unfolding to release Sojourner, asmall solar-powered rover, which rolled around the terrain for 83 days,

photographing and analysing the Martian rocks, before grinding to ahalt. Then, in September, a new orbiter spacecraft. Mars Global Surveyor, arrived to make adetailed photographic survey. In the decade since our explorations of Mars restarted, more landers, rovers and orbiters

have followed these pioneers. There have been

embarrassing failures, but more successes, and our view of the planet has been transformed once

again. Everything about Mars now seems more complex and more active. There are rivers and

gulleys that formed in geologically recent times.

m

0 X m

O

desert it was once thought to be, and

“ O

while space probes have shown Mars to

>

Earth have revealed how life can develop and thrive in far more hostile, perhaps even Mars-

MARS’ MOONS Deimos (lower left) and Phobos (lower right) are thought to be former asteroids. A true asteroid, 951 Gaspra (top), is shown for comparison.

seemed doomed to failure. The next US attempt. Mars Observer, in 1992, also met an ignominious

a

like, environments than was once thought possible.

> 7 0 C O

m

S PA C E

m

S TA R S

KtV CHRISTIAAN HUYGENS (I629-1695) utch astronomer and physicist Christiaan Huygens won his place in astronomical history for aseries of discoveries he made in the mid-17th century using his own self-made telescopes.

□

He was the first person to observe the surface markings of Mars, including Syrtis Major i and the ice at the south pole. He also correctly identified the structure of €

Saturn’s rings, and discovered Saturn’s giant moon. Titan.

In addition, Huygens played an important role in the development

jof calculus (a branch of maths), marshalled the evidence that light :was some form of wave, and

explored the way in which sound is perceived by the human ear. As a s e l f - t r a i n e d i n s t r u m e n t m a k e r,

he also developed an early form of microscope, pendulum clocks, and even adesign for an internal combustion engine.

for missions to Mars is

e s s

than half, NASA's Mariner

programme fared relatively well, being the first to reach Mars and Venus successfully. engineers into orbit and to

This housed the controlling electronics and provided abase to

the Moon, NASA turned its

which were attached an antenna

eaten by Soviet space

attention to the next challenge -the cameras, propulsion units and the exploration of Mars and Venus. A power source. series of missions was planned and aspace-craft called Mariner was All Mariners after 4had four solar developed to carry them out. Mariner was based on ahexagonal panels, apart from Mariner 10, which had two. The first five or octagonal “bus" (see Glossary).

The 412kg spacecraft was launched from

Cape Canaveral

0

aboard an AtlasCentaur rocket on 27 March

1969.

i

i

T

%

SCI-FI

\

MARS IN THE MOVIES sthe closest rocky planet in our solar system with A the tantalising possibility of sustaining life, it’s hardly surprising that Mars is aaperennial subject for s c i - fi m o v i e m a k e r s .

The first was ablack-and-white short, ATrip to Mars, produced by Thomas Edison in 1904, where a

professor makes amagic potion that sees him fly to Mars, then get blown back home by aMartian giant Amongst the more recent offerings is the Arnold Schwarzenegger film. Total Recall [^SSO], in which a

construction worker signs up for an imaginary holiday to Mars that goes horribly wrong. TOTAL RECALL Construction worker Douglas Quaid in the process of having aMars experience implanted in his memory the laboratory of the virtual holiday company, Rekall Inc. This

i n

award-winning film was based on the book We Can Remember It For You Wholesale, written by Philip KDick.

t

o

!

m

SURFACE

One of the

images of the disappointingly barren surface

captured by Mariner 4as it

passed within 9912km of the

planet.

> Z m u

i

O G L O S S A R Y

Mariners were launched by Atlas Agena rockets and the last five by Atlas-Centaur rockets.

dark features on the surface were

The Mariners were designed to be launched in pairs. Mariners 1 and 2were Venus probes

not canals as once claimed in the

When the storm cleared, though,

19th century.

Mariner 9circled Mars for 349

m a k e fi n a l

propulsion units, antenna and science

checks to the

instruments.

spacecraft before It is placed inside

the capsule for launch.

M a r i n e r 5 w a s a n o t h e r Ve n u s

Mars. Initially, aplanet-wide dust storm prevented the spacecraft from photographing the surface. in 1969, that made asuccessful So controllers on Earth delayed dual mission to Mars. They returned capturing any images until the dust over 200 images of the surface. The had settled, about two months later. pictures showed clearly that the

Cape Canaveral

Bus: The body shell of the spacecraft, ready to be fitted with power sources,

Te c h n i c i a n s a t

probe but Mariners 6and 7were identical spacecraft, both launched

days, transmittinj 7329 images, covering

and the first Mariners to Mars were 3and 4.

some 80% of Mars’

Mariner 3was lost when

surface. After

its launch vehicle’s nose

fairing failed to jettison

Robert Roddaril, pioneer of iiquid-fuelleif rocketry

But Mariner 4launched

successfully on 28 IMovember 1964

The following launch window o

and reached Mars on 14 July 1965 As it flew by, approaching as close as 9912km, it returned 22 images

was in May 1971, and while

of the Martian surface.

exhausting its altitude supply gas, the

spacecraft was shut off in October 1972. It is expected to continue to orbit Mars until at least

Mariner 8suffered alaunch

2022. The last in the programme

failure, its sister ship, Mariner 9

was Mariner 10, which visited

became the first probe to orbit

Venus and Mercury.

M RO IU NG EH R ®BREA KTAHR S9 R E V E L A T I O N S he images returned by Mariner 9revealed riverbeds suggesting that liquid water might well have flowed on the surface of the planet at one time -as well as craters and mountains. In addition, it captured images of agiant canyon system (the largest in the solar system), which was named in honour of the spacecraft, Valles Marineris. The probe also found evidence of wind and water erosion and deposition, weather fronts and fogs. It also took the opportunity, while Mars Itself was shrouded in dust, to turn away from the planet to

I

T

photograph Mars’ tiny moons, Phobos and Delmos.

MARINER 9Martian data was returned via the high-gain antenna dish.

> c n

m

V

(

The WONDERS MARS Every new mission to Mars

has shown greater and

greater detail of the planet's extraordinary surface. twasn’t until the Mars Global Surveyor m i s s i o n 1997 that high-quality images began to i n

r e v e a

the true beauty of the Red Planet.

The high-resolution cameras carried by ESA’ Mars Express and NASA’s Mars Reconnaissance

Oribiter (MRO), along with the cameras aboard the Mars Exploration Rovers, have taken imagery of the Martian surface to anew level. Data collected

by the MRO, for example, can show detail on Mars the size of adinner plate. 1

> m

0 >

|t^

spacecraft.

[ 5 ] V I C T O R I A C R AT E R

[3] DAO AND NIGER The point where the

An image taken by the Opportunity Rover of the rocky Cape Verde jutting

north-eastern Hellas

from the walls of the

impact crater basin and

Victoria crater.

'V

[61

[6] VALLES MARINERIS An artist's impression of Valles Marineris at dawn, with weak sunlight casting rays through the mist. Lying just south of the Martian equator, the valley is the result of tectonic activity several billion years ago with buffeting winds and flowing water having served

> G) ■-■m f

O

> m




south around midnight and remains visible all night. Mars reaches opposition every 780 days,

CD

but because its orbit is markedly elliptical not all

oppositions are equally favourable. When oppositions occur around the time of the planet’s perihelion, which will next occur in 2018, Mars can be less than 58 million km from

Earth. It then appears at its largest and can reach magnitude -2.9, rivalling Jupiter. At the other extreme, if Mars is near its

X I

^CROPS ANDCONFLICT M

O D

I'

I

ars is named after the

Roman god of war, for its

angry red colour was inevitably a s s o c i a t e d w i t h b l o o d s h e d . Ye t

Mars was originally abenign god

i ,

aphelion (farthest from the Sun), at the time of opposition, as in 2012 and 2027, then more

called Maris, who was linked with

than 100 million km can separate us and surface

Mars fathered Romulus, the

d e t a i l s a r e m o r e d i f fi c u l t t o m a k e o u t .

founder of Rome, and so was

n , k.AL a:

The list below gives the years when Mars is in opposition and hence close to Earth:

highly regarded by the Romans.

m m M

agriculture. According to legend.

The equivalent Greek war god was Ares. His children were Phobos

2 0 1 0

99.4 million km

2012 100.9 million km (farthest opposition) 2 0 1 4

92.9 million km

2 0 1 6

76.2 million km

2 0 1 8

57.7 million km (closest opposition)

2 0 2 0

62.6 million km

2 0 2 2

82.3 million km

P O P S

96.2 million km^

I

A

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i

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(“fear”) and Deimos (“terror”). after whom the two moons of the

I

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planet are named.

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Mars is easily located against the zodiac constellations. Its oppositions over the next

six years is shown above, starting in Leo in

June 2008 and ending in Virgo in June 2014.

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@GILBERT LEVIN

does. In many ways, this mix would be an ideal internal fluid for the cells of microbes living in the extremely cold Martian soil. The discovery of "extremophile" bacteria that survive the intense cold of Antarctica in just this

(1924-present)

r

ilbert Levin trained as an engineer at Johns Hopkins University, and worked in public health before returning there in 1960 to complete adoctorate in environmental engineering. As part of his doctoral research, he developed the “labelled«release” system for

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detecting microbes in soil samples on Earth. Achance meeting with the NASA administrator 1960 led to his involvement

in development of the Viking experiments, and the results convinced him that the mission

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V.

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was an enormous surprise to the researchers who first discovered them just afew decades ago. And it has revolutionized the way astronomers think

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^by the other Viking experiments. When the cells

had indeed detected life on

of dying bacteria break down, the H2O2 released

Mars. Since 1967, Levin

Iwould react with and destroy organic molecules,

has run his own technology company, Biospherix, developing innovative food additives and medical treatments.

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way (though using other chemicals as antifreeze)

about life on other planets. One major benefit of the "antifreeze” theory is that it not only means life might exist on Mars, but also explains the negative results obtained

T. Keith Glennan at aparty in

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■effectively wiping away the evidence and keeping

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Ithesoil’sorganiccontenttoaminimum.

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KILLER PROBE?

LEVIN Developed the Viking Mars life detection experiment.

not biological, caused by some molecule in the soil

sample reacting with the first injection of nutrients. In response to the negative news, some scientists made excuses -perhaps the retro-rockets from the landers had sterilized the soil on which they landed -and some questioned the methodology, but most accepted the basic conclusions.

RETRO ROCKETS Blasts from the rocket motors as landers descend could

destroy any signs of life in the ground below. This could have affected

Viking data, and Phoenix (pictured) will also have to take this into account.

In early 2007, two scientists gave apresentation to the American Astronomical Society conference in Seattle on this subject. Dirk Schulze-Makuch and Joop Houtkooper explained how Martian bacteria

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might survive using awater/peroxide antifreeze mix

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and also how the labelled-release experiment could

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have killed them.

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Sudden exposure to liquid water, such as that used as abasis for Viking’s nutrient solution, would cause antifreeze to expand suddenly.

EXTREMOPHILE BACTERIA

However, afew isolated voices suggested a different interpretation. Their theory cannot yet be proven, but recent discoveries about the wide

variety of life that exists on Earth -especially living in hostile conditions, such as extreme heat or cold

-suggest that it should not be discounted either. The leading advocate of this view is Gilbert Levin (see Space Stars). He has suggested a variety of mechanisms that might give abiological explanation for the observed results, many of which assume the presence of hydrogen peroxide (H2O2) in the soil. This chemical is highly reactive (it was used as apropellant in some of the first rockets), and is also adisinfectant, so one might assume it would kill any bacteria. But it can be stabilised with avariety of chemicals, and is found

inside many living creatures, including mammals. What’s more, amix of H2O2 and water can act as "antifreeze”

remaining liquid at temperatures down to -55°C. When it does solidify, it does not form harmful ice crystals the way pure water

bursting the cell walls and killing the microbes. G L O S S A R Y

Isotope: Aform erf ^

element withmorsor.j less mass than usual. ThiscanmakeJtun.^ resulting in

In this way, the build-up of radioactive gas that was detected following the initial injection of nutrients could possibly have been a"last gasp” from Martian bacteria that were destroyed by the experiment itself. 23

ISSUE

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been sculpted dramatically by volcanic eruptions and cratering.

"Explore Mars through cameras and instruments packed into two Viking orbiters and landers.

"Track the path of Mars and other C€ superior planets around the sky.

Eaglemoss Publications Ltd, Beaumont House, Avonmore Road, London W14 STS

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APRECISION-ENGINEERED ORRERY

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featuring vast CANYONS and VOLCANOES

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"The orrery is aprecision-engineered kit. It must be assembled and handled

^YOUR SOLAR SYSTEM MODEL

See how the superior planets follow long paths around the sky, often with complex loops and reversals.

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SOLAR SYSTEM GUIDE The rocks of Mars reveal its complex geological history, from cratering to volcanic eruptions.

MISSIONS

with care to prevent damage to its parts, and stored or displayed safely to ensure no parts are lost. "Never use liquids or solvents to clean the parts. For best care, use the polishing cloth and dusting brushes supplied with the toolkit (free to subscriptions customers). "When assembling parts, lay them on a

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materials.

The Viking probes were sent to discover if there is life on Mars, but was the question really answered?

IMAGE GALLERY Dramatic images of the volcanoes, lava streams and boulders that suggest recent volcanic activity on Mars. 16

T H E S TO R Y O F A S T R O N O M Y r

What did early sky-watching astrologers see that convinced them our fate is revealed in the stars?

2 0

♦

S TA R M A P Focus on two mythical twins. Castor and Pollux -together forming Gemini -and on Cancer, the crab.

UNEXPLAINED

#

11

CREDITS

Are you ahigh achiever? If so, could it be that Mars has been influential in your development? C O N S U LTA N T E D I T O R : G I L E S S PA R R O W

IMAGES: FC Science Photo

Library/Chris Butler; 2-3 (r) Eaglemoss/Julian Fletcher; 4(tl)

♦Galaxy Picture Library/Damian

E N D O R S E D B Y : S I R PAT R I C K M O O R E C B E F R S

ENCOURAGED BY: THE INTERNATIONAL ASTRONOMICAL UNION

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i

Stapleton Collection, (br) Alamy/ Mary Evans Picture Library; 2021 (tl) NASA/STSd/Andrew Fruchter, (tr) NOAO/AURA/NSF,

Peach, (b) Tunc Tezel; 5(tl) Galaxy

(bl,tc,br) Pikaia Imaging; 22(tl)

Picture Library/Dave Tyler, (b) Pikaia Imaging; 6-7(l,br) NASA/

Corbis UK/Jean-Yves Ruszniewski/

JPL, (cr) ESA/DLR/FU Berlin/G Neukum; 8-9(cl) NASA/JPL, (tc,cr) ESA/DLR/FU Berlin/G Neukum, (b)

Pikaia Imaging; 10-11 NASA/JPL/ Z m

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purchase, Mr and Mrs Edgar B Whitcomb fund, (tr) Rex Features/ Canadian Press, (br) Pikaia Imaging.

.Imaging; 16(tr) Bridgeman Art

Library/British Museum, London, (b) Topfoto/British Museum, REPRO: Stormcreative London/HIP; 17 (t) Alamy/North Wind Picture Archives, (br) Alamy/ Publishing Limited Mary Evans Picture Archive; 18(tr)

.Alamy/Mary Evans Picture Library; PRINTING: Century Litho (Truro) 19(tr) Bridgeman Art Library/The Limited Eaglemoss Publications Ltd, "

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Planets with orbits beyond " the Earth follpw their own

he path which any object in the sola?' system takes ajpound the sky depend the relatioViship of its own orbit to our .

longpathsfaroiJ^dthesky,^point of view on Earth. Mercury and Venus lie "

system model, focusing

on*Earth,^the planets Mars, Ceres, Jupiter and

Saturn are .arranged at often Involving complex Ipops. cclosertotf^Sunthandoesourownplanet.'So, conj uncti o n (farthes t * and re’^ersals. Together ^from our point of view, their orbits are re^triaed to 1f-from Earth), opposition

they are known as the

superior fSlanets:.

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simple loops on either side of the Sun, and they* are only ever seen in the rporning 6r eVeffing skies. They are known as the inferior planets.

(closest to Earth), ^

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western quadrature.*

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■

G L O S S A R Y

Synodic year: The orbital period of aplanet

INFO

CHANGING APPEARANCES

measured relative to Earth -the time between

r hlle the inferior planets can go through acomplex cycle of phases as we see different amounts of their sunlit hemispheres, the sunlit half of asuperior planet is almost always facing towards us, so they usually appear as perfect discs. The only exception to this is Mars, which is close enough to us that at certain times we can see alittle way "around the back” onto the Martian night side. At this point the planet appears gibbous, like our own Moon acouple of days from

s u c c

w

issive oppositions or

conjunctions.

Sidereal year: Aplanet’s orbital period measured relative to the Sun and stars -the time it takes to return to the same

point regj ‘ d i e s s o f i t s

position relative to Earth. L

full. This is most noticeable when Mars is at

quadrature. GIBBOUS MARS Less than 50 percent of the disc visible from Earth is in shadow during the gibbous phase of Mars.

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The planets beyond Earth -Mars, Jupiter, Saturn, Uranus and Neptune -have adifferent kind of path. Their orbits encircle Earth’s own, so they can travel

all around the sky and are not hitched to the Sun. In fact, at times they can appear directly opposite the Sun, rising as it sets and remaining visible all night. These are the superior planets -although asteroids, comets and dwarf planets farther from the Sun can also follow superior-type orbits. The superior planets take longer than Earth to

Over the course of aplanet’s “synodic” year (see Glossary), it moves eastwards around the heavens, emerging from conjunction to become visible

in the western sky shortly after sunset. It then increases its distance from the Sun until it is visible

into the night. By opposition, the planet is rising as the Sun sets, so it can be seen all night. But, as the time of its rising gets ever later, it eventually becomes amorning object, rising only just before

A P PA R E N T S I Z E The diameter of Mars as

it appears in the night sky from Earth is six times larger at opposition compared to when it is at adistant conjunction.

These images are of Mars seen at varying apparent

sizes during the 20052006 opposition.

orbit the Sun -their orbits are larger and they travel more slowly. For comparison. Earth moves along its orbit at 29.8 kilometres per second, while Mars moves at 24.1km/s and Saturn at 9.5km/s. As each

planet orbits the Sun, it traces apath against the stars. Because the solar system is fairly flat, with the orbits of the planets all roughly on aplane with Earth’s, this track stays close to the ecliptic -the apparent path of the Sun’s motion around the sky. As aresult, the planets, like the Sun itself, are mostly found in the band of zodiac constellations, which the ecliptic happens to pass through. POSITIONS IN THE SKY

Four positions on asuperior orbit have special significance in the planet’s relationship with Earth. At opposition, the planet lies precisely opposite

the sunrise and visible only in pre-dawn skies.

the Sun as seen from our own world, so the planet

Because our planet is unlikely to be in precisely the

is visible all night. At conjunction, the planet lies beyond the Sun as seen from Earth -the two are

same position on its own orbit when the superior

more-or-less lined up in our sky (depending on

faster-moving Earth has to catch up in order to reach anew conjunction. So asynodic year can

the tilt of the planet’s own orbit), and the planet cannot be seen at night at all. Quadratures mark points where the angle between Earth, Sun and planet is 90 degrees (see How It Works).

Finally it returns to conjunction with the Sun. Earth’s own movements add complications.

planet has completed one circuit of the Sun, the

be longer than the planet’s sidereal year relative to the Sun and stars (see Glossary). What’s more.

Earth’s “overtaking” manoeuvres as it speeds past

RETROGRADE MOTION

About every two years. Earth passes Mars as

they orbit the Sun. During this time. Mars (digitally stacked in this image) traces out a"retrograde motion" loop in the sky.

aslower moving outer world around opposition can cause the planet to make an apparent backward loop in the sky -a"retrograde motion".

The major change in asuperior planet’s appearance is one of size. At opposition, the Earth

lies on astraight line between the Sun and the planet, so the planet is at its closest to us. At conjunction. Earth and the planet lie on opposite sides of the Sun and are farthest away from each other. The difference in distance between the two extremes is equivalent to the diameter of Earth’s orbit -300 million km.

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