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Britannica Illustrated Science LibraryBritannica Illustrated Science Library

UNIVERSEUNIVERSE

© 2008 Editorial Sol 90All rights reserved.

Idea and Concept of This Work: Editorial Sol 90

Project Management: Fabián Cassan

Photo Credits: Corbis, ESA, Getty Images, Graphic News,NASA, National Geographic, Science Photo Library

Illustrators: Guido Arroyo, Pablo Aschei, Gustavo J. Caironi,Hernán Cañellas, Leonardo César, José Luis Corsetti, VaninaFarías, Joana Garrido, Celina Hilbert, Isidro López, DiegoMartín, Jorge Martínez, Marco Menco, Ala de Mosca, DiegoMourelos, Eduardo Pérez, Javier Pérez, Ariel Piroyansky, ArielRoldán, Marcel Socías, Néstor Taylor, Trebol Animation, JuanVenegas, Coralia Vignau, 3DN, 3DOM studio

Composition and Pre-press Services: Editorial Sol 90

Translation Services and Index: Publication Services, Inc.

Portions © 2008 Encyclopædia Britannica, Inc.Encyclopædia Britannica, Britannica, and the thistle logo areregistered trademarks of Encyclopædia Britannica, Inc.

Britannica Illustrated Science Library Staff

EditorialMichael Levy, Executive Editor, Core EditorialJohn Rafferty, Associate Editor, Earth SciencesWilliam L. Hosch, Associate Editor, Mathematics and

ComputersKara Rogers, Associate Editor, Life SciencesRob Curley, Senior Editor, Science and TechnologyDavid Hayes, Special Projects Editor

Art and CompositionSteven N. Kapusta, DirectorCarol A. Gaines, Composition SupervisorChristine McCabe, Senior Illustrator

Media AcquisitionKathy Nakamura, Manager

Copy DepartmentSylvia Wallace, DirectorJulian Ronning, Supervisor

Information Management and RetrievalSheila Vasich, Information Architect

Production ControlMarilyn L. Barton

ManufacturingKim Gerber, Director

Britannica IllustratedScience LibraryBritannica IllustratedScience Library

Encyclopædia Britannica, Inc.

Jacob E. Safra, Chairman of the Board

Jorge Aguilar-Cauz, President

Michael Ross, Senior Vice President, Corporate Development

Dale H. Hoiberg, Senior Vice President and Editor

Marsha Mackenzie, Director of Production

International Standard Book Number (set): 978-1-59339-797-5

International Standard Book Number (volume): 978-1-59339-798-2

Britannica Illustrated Science Library: Universe 2008

Printed in China

www.britannica.com

Contents PICTURE ON PAGE 1Image of a planetary nebula.Planetary nebulae are amongthe most photogenic objectsin astronomy.

What Is theUniverse?Page 6

What Is in theUniverse?Page 18

The SolarSystemPage 38

The Earthand the MoonPage 66

Observingthe UniversePage 80

There was a time when people believedthat the stars were bonfires lit byother tribes in the sky, that the

universe was a flat plate resting on the shellof a giant turtle, and that the Earth,according to the Greek astronomer Ptolemy,was at the center of the universe. From themost remote of times, people have beencurious about what lies hidden beyond thecelestial sphere. This curiosity has led themto build telescopes that show with clarityotherwise blurry and distant objects. In thisbook you will find the history of the cosmosillustrated with spectacular images thatshow in detail how the cosmos was formed,the nature of the many points of light thatadorn the night sky, and what lies ahead.You will also discover how the suns thatinhabit space live and die, what dark matterand black holes are, and what our place is inthis vastness. Certainly, the opportunity to

compare the destiny of other worlds similarto ours will help us understand that for thetime being there is no better place than theEarth to live. At least for now.

In the Milky Way—according tomathematical and physicalcalculations—there are more than 100

billion stars, and such a multitude leads tothe question: Is it possible that our Sun isthe only star that possesses an inhabitedplanet? Astronomers are more convincedthan ever of the possibility of life in otherworlds. We just need to find them. Readingthis book will let you become betteracquainted with our neighbors in the solarsystem—the other planets—and the mostimportant characteristics that distinguishthem. All this information that explores themysteries of space is accompanied byrecent images captured by the newesttelescopes. They reveal many details aboutthe planets and their satellites, such as thevolcanoes and craters found on the surfaceof some of them. You will also learn moreabout the asteroids and comets that orbitthe Sun and about Pluto, a dwarf planet,which is to be visited by a space probe for

the first time. Less than a decade ago,astronomers began observing frozen worlds,much smaller than a planet, in a region ofthe solar system called the Kuiper belt. Weinvite you to explore all of this. The imagesand illustrations that accompany the textwill prove very helpful in studying andunderstanding the structure of all the visibleand invisible objects (such as dark matter)that form part of the universe. There arestellar maps showing the constellations, thegroups of stars that since ancient times haveserved as a guide for navigation and for thedevelopment of calendars. There is also areview through history: from Ptolemy, whothought the planets orbited around theEarth, and Copernicus, who put the Sun inthe center, and Galileo, the first to aim atelescope skyward, up to the most recentastronomical theories, such as those ofStephen Hawking, the genius of space andtime who continues to amaze with hisdiscoveries about the greatest mysteries ofthe cosmos. You will find these and manymore topics no matter where you look in thisfantastic book that puts the universe and itssecrets in your hands.

The Secrets ofthe Universe

CONE NEBULAThis nebula got its namefrom its cone shape, asshown in the image.

What Is the Universe?

The universe is everything thatexists, from the smallestparticles to the largest ones,together with all matter andenergy. The universe includes

visible and invisible things, such as darkmatter, the great, secret component ofthe cosmos. The search for dark matteris currently one of the most importanttasks of cosmology. Dark matter may

literally determine the density of all ofspace, as well as decide the destiny ofthe universe. Did you know that, secondby second, the universe grows andgrows? The question that astronomers

are asking—the question that concernsthem the most—is how much longer theuniverse can continue to expand like aballoon before turning into somethingcold and dark.

X-RAY OF THE COSMOS 8-9

THE INSTANT OF CREATION 10-13

EVERYTHING COMES TO AN END 14-15

THE FORCES OF THE UNIVERSE 16-17

DARK MATTEREvidence exists that dark matter, though invisibleto telescopes, betrays itself by the gravitationalpull it exerts over other heavenly bodies.

UNIVERSE 98 WHAT IS THE UNIVERSE?

The universe, marvelous in its majesty, is an ensemble of a hundredbillion galaxies. Each of these galaxies (which tend to be found inlarge groups) has billions of stars. These galactic concentrations

surround empty spaces, called cosmic voids. The immensity of thecosmos can be better grasped by realizing that the size of our fragileplanet Earth, or even that of the Milky Way, is insignificantcompared to the size of the remainder of the cosmos.

Originating nearly 14 billion years agoin an immense explosion, the universe

today is too large to be able to conceive. Theinnumerable stars and galaxies that populate itpromise to continue expanding for a long time.Though it might sound strange today, for manyyears, astronomers thought that the Milky Way,where the Earth is located, constituted the entireuniverse. Only recently—in the 20th century—was outerspace recognized as not only much vaster than previouslythought but also as being in a state of ongoing expansion.

The Universe

NEAR STARS Found closerthan 20 light-years from theSun, they make up our solarneighborhood.

2.

NEIGHBORS Within a spaceof one million light-years,we find the Milky Way andits closest galaxies.

3.NEAREST GALAXIES. At a scaleof one hundred million light-years,the galactic clusters nearest tothe Milky Way can be seen.

5.

FILAMENTS. From five billionlight-years away, the immensity ofthe cosmos is evident in itsgalactic filaments, each one hometo millions and millions of galaxies.

7.SUPERCLUSTERS. Within adistance of a billion light-years,groups of millions of galaxies,called superclusters, can be seen.

6.

LOCAL GROUP. Tenmillion light-years awayis Andromeda, theclosest to the Earth.

4.

EARTH Originated, togetherwith the solar system, whenthe universe was already 9.1billion years old. It is the onlyknown planet that is home to life.

1.

EARTH

Neptune

G51-15

Ross128

Lalande21185

Wolf359

Luyten’sStar

Procyon

Uranus

Saturn

Jupiter

Pluto

SUNAlphaCentauri

Sirius

270°

90°

180°

0.5

0°

180°

0°

12.5

EpsilonEridani

L372-58

L726-8

L725-32

EpsilonIndi

Lacaille9352Ceti

7.5

2.5

Struve2398

Ross248

Ross154

Groombridge34

61 Cygni

Bernard’s Star

L789-6

L789-6

0°

SextansDwarf

UrsaMinor Dwarf

Leo A

Leo I Leo II

Andromeda I

Sextans BSextans A

AntilaDwarf

NGC3109

DracoDwarf

SagittariusDwarf

TucanaDwarf

PhoenixDwarf

CetusDwarf Sagittarius

IrregularDwarf

AquariusDwarf

LGS 3

PegasusDwarf

IC1613

WLM

CanisMajor

SmallMagellanicCloud

LargeMagellanicCloud

CarinaDwarf

MILKY WAY

MILKY WAY

NGC6822

Triangle

Andromeda

M32

M110

NGC185

NGC147

IC 10

0.120.25

0.37

1.22.5

3.7

0°

180°

0°

180°

NGC7582

NGC6744

CapricornusSupercluster

Pavo-IndusSupercluster

SculptorSupercluster

SculptorVoid

Pisces-CetusSuperclusters

Pisces-PerseusSupercluster

ComaSupercluster

CentaurusSupercluster

HerculesSupercluster

ShapleySupercluster

BoötesVoid

LeoSupercluster

Ursa Major Supercluster

BoötesSupercluster

Corona Borealis Supercluster

Hydra

HorologiumSuperclusters Columba

Supercluster

NGC1023

NGC2997

NGC5128

NGC5033

NGC4697

12.5

25

37.5

50

1,000

750

250

Dorado

Sculptor

Maffei

M81

M101

Leo I

Canis

Ursa Major Group

VirgoGroup

Leo III Group

Virgo III Group

FornaxCluster

EridanusCluster

LOCALGROUP

VIRGO

SextansSupercluster

X-Ray of the Cosmos

100 billionThe total number of galaxies that exist,indicating that the universe is both largerand older than was previously thought