About the pagination of this eBook Due to the unique page numbering scheme of this book, the electronic pagination of the eBook does not match the pagination of the printed version. To navigate the text, please use the electronic Table of Contents that appears alongside the eBook or the Search function. For citation purposes, use the page numbers that appear in the text. UNIVERSEUNIVERSE Britannica Illustrated Science Library Encyclopædia Britannica, Inc. Chicago ■ London ■ New Delhi ■ Paris ■ Seoul ■ Sydney ■ Taipei ■ Tokyo Britannica Illustrated Science Library © 2008 Editorial Sol 90 All 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, Vanina Farías, Joana Garrido, Celina Hilbert, Isidro López, Diego Martín, Jorge Martínez, Marco Menco, Ala de Mosca, Diego Mourelos, Eduardo Pérez, Javier Pérez, Ariel Piroyansky, Ariel Roldán, Marcel Socías, Néstor Taylor, Trebol Animation, Juan Venegas, 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 are registered trademarks of Encyclopædia Britannica, Inc. Britannica Illustrated Science Library Staff Encyclopædia Britannica, Inc. Editorial Jacob E. Safra, Chairman of the Board Michael Levy, Executive Editor, Core Editorial John Rafferty, Associate Editor, Earth Sciences Jorge Aguilar-Cauz, President William L. Hosch, Associate Editor, Mathematics and Computers Michael Ross, Senior Vice President, Corporate Development Kara Rogers, Associate Editor, Life Sciences Rob Curley, Senior Editor, Science and Technology Dale H. Hoiberg, Senior Vice President and Editor David Hayes, Special Projects Editor Marsha Mackenzie, Director of Production Art and Composition Steven N. Kapusta, Director Carol A. Gaines, Composition Supervisor Christine McCabe, Senior Illustrator International Standard Book Number (set): Media Acquisition 978-1-59339-797-5 Kathy Nakamura, Manager International Standard Book Number (volume): 978-1-59339-798-2 Copy Department Britannica Illustrated Science Library: Universe 2008 Sylvia Wallace, Director Julian Ronning, Supervisor Printed in China Information Management and Retrieval Sheila Vasich, Information Architect Production Control Marilyn L. Barton Manufacturing Kim Gerber, Director www.britannica.com Universe PICTURE ON PAGE 1 Image of a planetary nebula. Contents Planetary nebulae are among the most photogenic objects in astronomy. What Is the Universe? Page 6 What Is in the Universe? Page 18 The Solar System Page 38 The Earth and the Moon Page 66 Observing the Universe Page 80 CONE NEBULA This nebula got its name from its cone shape, as shown in the image. compare the destiny of other worlds similar the first time. Less than a decade ago, The Secrets of to ours will help us understand that for the astronomers began observing frozen worlds, time being there is no better place than the much smaller than a planet, in a region of Earth to live. At least for now. the solar system called the Kuiper belt. We the Universe invite you to explore all of this. The images n the Milky Way—according to and illustrations that accompany the text mathematical and physical will prove very helpful in studying and here was a time when people believed I calculations—there are more than 100 understanding the structure of all the visible that the stars were bonfires lit by billion stars, and such a multitude leads to and invisible objects (such as dark matter) T other tribes in the sky, that the the question: Is it possible that our Sun is that form part of the universe. There are universe was a flat plate resting on the shell the only star that possesses an inhabited stellar maps showing the constellations, the of a giant turtle, and that the Earth, planet? Astronomers are more convinced groups of stars that since ancient times have according to the Greek astronomer Ptolemy, than ever of the possibility of life in other served as a guide for navigation and for the was at the center of the universe. From the worlds. We just need to find them. Reading development of calendars. There is also a most remote of times, people have been this book will let you become better review through history: from Ptolemy, who curious about what lies hidden beyond the acquainted with our neighbors in the solar thought the planets orbited around the celestial sphere. This curiosity has led them system—the other planets—and the most Earth, and Copernicus, who put the Sun in to build telescopes that show with clarity important characteristics that distinguish the center, and Galileo, the first to aim a otherwise blurry and distant objects. In this them. All this information that explores the telescope skyward, up to the most recent book you will find the history of the cosmos mysteries of space is accompanied by astronomical theories, such as those of illustrated with spectacular images that recent images captured by the newest Stephen Hawking, the genius of space and show in detail how the cosmos was formed, telescopes. They reveal many details about time who continues to amaze with his the nature of the many points of light that the planets and their satellites, such as the discoveries about the greatest mysteries of adorn the night sky, and what lies ahead. volcanoes and craters found on the surface the cosmos. You will find these and many You will also discover how the suns that of some of them. You will also learn more more topics no matter where you look in this inhabit space live and die, what dark matter about the asteroids and comets that orbit fantastic book that puts the universe and its and black holes are, and what our place is in the Sun and about Pluto, a dwarf planet, secrets in your hands. this vastness. Certainly, the opportunity to which is to be visited by a space probe for DARK MATTER X-RAY OF THE COSMOS 8-9 Evidence exists that dark matter, though invisible to telescopes, betrays itself by the gravitational THE INSTANT OF CREATION 10-13 pull it exerts over other heavenly bodies. What Is the Universe? EVERYTHING COMES TO AN END 14-15 THE FORCES OF THE UNIVERSE 16-17 he universe is everything that visible and invisible things, such as dark literally determine the density of all of are asking—the question that concerns exists, from the smallest matter, the great, secret component of space, as well as decide the destiny of them the most—is how much longer the particles to the largest ones, the cosmos. The search for dark matter the universe. Did you know that, second universe can continue to expand like a T together with all matter and is currently one of the most important by second, the universe grows and balloon before turning into something energy. The universe includes tasks of cosmology. Dark matter may grows? The question that astronomers cold and dark. 8 WHAT IS THE UNIVERSE? UNIVERSE 9 Corona Borealis Supercluster Capricornus Supercluster SUPERCLUSTERS. Within a FILAMENTS. From five billion X-Ray of the Cosmos distance of a billion light-years, light-years away, the immensity of 6. groups of millions of galaxies, 7. the cosmos is evident in its called superclusters, can be seen. galactic filaments, each one home he universe, marvelous in its majesty, is an ensemble of a hundred to millions and millions of galaxies. Hercules billion galaxies. Each of these galaxies (which tend to be found in Supercluster Boötes Void Boötes T large groups) has billions of stars. These galactic concentrations Supercluster 180° Pavo-Indus surround empty spaces, called cosmic voids. The immensity of the Supercluster cosmos can be better grasped by realizing that the size of our fragile planet Earth, or even that of the Milky Way, is insignificant Shapley Centaurus Supercluster compared to the size of the remainder of the cosmos. Supercluster Sculptor Sculptor Supercluster Void VIRGO Coma Ursa Major Supercluster Supercluster 250 Pisces-Cetus Superclusters Hydra Leo 750 Supercluster 1,000 Pisces-Perseus 1. Supercluster Virgo III 0° Group EARTH Originated, together with the solar system, when The Universe the universe was already 9.1 Originating nearly 14 billion years ago Sextans billion years old. It is the only Supercluster in an immense explosion, the universe known planet that is home to life. today is too large to be able to conceive. The innumerable stars and galaxies that populate it 180° promise to continue expanding for a long time. Horologium EARTH Though it might sound strange today, for many Superclusters Columba Supercluster Pluto years, astronomers thought that the Milky Way, NGC Neptune NGC where the Earth is located, constituted the entire 6744 LOCAL 7582 GROUP NGC universe. Only recently—in the 20th century—was outer Jupiter NGC 5033 Uranus Virgo NGC space recognized as not only much vaster than previously 5128 M101 Canis Group 4697 Saturn thought but also as being in a state of ongoing expansion. Sculptor 12.5 Maffei 25 M81 37.5 Ursa Major NGC Leo I Group 50 1023 NGC 2997 Dorado 0° Fornax NEAR STARS Found closer Cluster than 20 light-years from the Eridanus Sextans B Leo III Sun, they make up our solar Cluster Group 2. Sextans A neighborhood. Ross Lalande G51-15 128 21185 Struve At a scale Wolf NEAREST GALAXIES. 2398 359 of one hundred million light-years, the galactic clusters nearest to 12.5 Leo A 5. Procyon Within a space 90° NEIGHBORS the Milky Way can be seen. Luyten’s 7.5 of one million light-years, NGC Star Bernard’s 2.5 we find the Milky Way and 3109 Antila Star 3.