Front Matter

Cambridge University Press 978-1-108-43138-5 — The Cosmos 5th Edition Frontmatter More Information

The Cosmos Astronomy in the New Millennium

FIFTH EDITION

The Fifth Edition of The Cosmos: Astronomy in the New Millennium provides you with the fundamentals of astronomical knowledge that have been built up over decades, with an expanded discussion of the incredible advances that are now taking place in this fast-paced field, such as New Horizons’ flyby of Pluto, exoplanets, “dark matter,” and the direct detection of gravitational waves by LIGO. Written in a clear and easily understandable style, this textbook has been thoroughly revised to include (among other things) updated data and figures, new images from recent space missions and telescopes, the latest discoveries on supernovae, and new observations of the region around the four-million-solar-mass black hole at the center of our Milky Way Galaxy.

Jay M. Pasachoff, Field Memorial Professor of Astronomy at Williams College, teaches the astronomy survey course. He is also Director of the Hopkins Observatory there. He received his undergraduate and grad- uate degrees from Harvard and then had postdoctoral fellowships at the Harvard College Observatory and the California Institute of Technology, where he has also had recent sabbatical leaves. He now has a visiting appointment at the Carnegie Observatories. He has observed 70 solar eclipses. He also studies occultations of stars by Pluto and other objects in the outer Solar System. Pasachoff is Chair of the Working Group on Eclipses of the International Astronomical Union and was Chair of the American Astronomical Society’s Historical Astronomy Division. He is also co-editor of Teaching and Learning Astronomy (2005) and Innovation in Astronomy Education (2008). He received the American Astronomical Society’s Education Prize (2003); the Janssen Prize from the Société Astronomique de France (2012); and the Richtmyer Memorial Lecture Award, American Association of Physics Teachers (2017). Asteroid (5100) Pasachoff is named after him.

Alex Filippenko is a Professor of Astronomy, and the Richard & Rhoda Goldman Distinguished Professor in the Physical Sciences, at the University of California, Berkeley. He received his undergraduate degree from the University of California, Santa Barbara (1979) and his doctorate from the California Institute of Technology (1984). His primary areas of research are exploding stars, gamma-ray bursts, active galaxies, black holes, and observational cosmology. Filippenko was the only person to have been a member of both teams that revealed the Nobel-worthy accelerating expansion of the Universe. He is one of the world’s most highly cited astronomers and was elected to the National Academy of Sciences (2009). Filippenko has won many prestigious teaching awards, including the Carnegie/CASE National Professor of the Year among doctoral institutions (2006). He has appeared frequently on science newscasts and television documentaries, especially The Universe series. He received the Carl Sagan Prize for Science Popularization (2004). He enjoys world travel and observing total solar eclipses (16, all successfully).

An artist’s conception of two black holes, GW170104, as they merged, similar to the ones detected by the Laser Interferometer Gravitational-wave Observatory (LIGO). Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

The Cosmos

Astronomy in the New Millennium

FIFTH EDITION

Jay M. Pasachoff Williams College, Massachusetts Alex Filippenko University of California, Berkeley

University Printing House, Cambridge CB2 8BS, United Kingdom One Liberty Plaza, 20th Floor, New York, NY 10006, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia 314–321, 3rd Floor, Plot 3, Splendor Forum, Jasola District Centre, New Delhi – 110025, India 79 Anson Road, #06–04/06, Singapore 079906

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www.cambridge.org Information on this title: www.cambridge.org/9781108431385 © Jay M. Pasachoff and Alex Filippenko 2019 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. Fourth edition published in 2013. The previous edition (The Cosmos, 3rd Edition) was published in 2007 by Brooks/Cole Cengage. Printed and bound in Great Britain by Clays Ltd, Elcograf S.p.A. A catalog record for this publication is available from the British Library. ISBN 978-1-108-43138-5 Paperback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party Internet Web sites referred to in this publication and does not guarantee that any content on such Web sites is, or will remain, accurate or appropriate.

Contents

Preface xix

1. A Grand Tour of the Heavens 1 2. Light, Matter, and Energy: Powering the Universe 23 3. Light and Telescopes: Extending Our Senses 41 4. Observing the Stars and Planets: Clockwork of the Universe 75 5. Gravitation and Motion: The Early History of Astronomy 107 6. The Terrestrial Planets: Earth, Moon, and Their Relatives 133 7. The Jovian Planets: Windswept Giants 189 8. Pluto, Comets, Asteroids, and Beyond 225 9. Our Solar System and Others 263 10. Our Star: The Sun 289 11. Stars: Distant Suns 317 12. How the Stars Shine: Cosmic Furnaces 357 13. The Death of Stars: Recycling 381 14. Black Holes: The End of Space and Time 415 15. The Milky Way: Our Home in the Universe 447 16. A Universe of Galaxies 479 17. Quasars and Active Galaxies 523 18. Cosmology: The Birth and Life of the Cosmos 553 19. In the Beginning 589 20. Life in the Universe 623 Epilogue 644

Appendix 1/2. Measurement Systems/Basic Constants 645 Appendix 3. Planets and Dwarf Planets 647 Appendix 4. The Brightest Stars 649 Appendix 5. The Nearest Stars 651 Appendix 6. The Messier Catalogue 654

vi Contents

Appendix 7. The Constellations 656 Appendix 8. Star Names 658

Selected reading 661 Glossary 668 Index 685

Detailed Contents

Preface xix

1. A Grand Tour of the Heavens 1 1.1 Peering Through the Universe: A Time Machine 2 1.2 How Do We Study Things We Can’t Touch? 2 Figure It Out 1.1 Keeping Track of Space and Time 3 Figure It Out 1.2 Scientiﬁc Notation 3 1.3 Finding Constellations in the Sky 5 1.3a The Autumn Sky 6 Star Party 1.1 Using the Sky Maps 7 1.3b The Winter Sky 9 1.3c The Spring Sky 10 1.3d The Summer Sky 10 1.4 How Do You Take a Tape Measure to the Stars? 11 A Closer Look 1.1 A Sense of Scale: Measuring Distances 12 1.5 The Value of Astronomy 14 1.5a The Grandest Laboratory of All 14 1.5b Origins 15 1.6 What Is Science? 16 1.7 Why Is Science Far Better Than Pseudoscience? 17

2. Light, Matter, and Energy: Powering the Universe 23 2.1 Studying a Star Is Like Looking at a Rainbow 24 Credit: NASA, ESA, and B. Sunnquist J. Mack (STScI). Acknowledgment: NASA, ESA, and J. Lotz (STScI) the HFF Team Figure It Out 2.1 The Nature of Light 24 Asteroid trails, curved because of parallax across an image 2.2 “Blackbodies” and Their Radiation 26 of a cluster of galaxies in Hubble Frontier Field Abell 370. Figure It Out 2.2 Blackbody Radiation and Wien’s Law 26 Figure It Out 2.3 Blackbody Radiation and the 3.5 Amateurs Are Participating 53 Stefan–Boltzmann Law 27 3.6 Glorious Hubble After Initial Trouble 54 2.3 What Are Those Missing Colors and Where Are They? 28 3.7 You Can’t Look at the Sun at Night 56 2.4 The Story Behind the Bohr Atom 30 3.8 How Can You See the Invisible? 57 2.5 The Doppler Effect and Motion 33 3.8a X-ray and Gamma-ray Telescopes 57 Figure It Out 2.4 Temperature Conversions 35 3.8b Telescopes for Ultraviolet Wavelengths 60 3.8c Infrared Telescopes 60 3. Light and Telescopes: Extending Our Senses 41 3.8d Radio Telescopes 62 3.1 The First Telescopes for Astronomy 41 Figure It Out 3.3 Angular Resolution of a 3.2 How Do Telescopes Work? 43 Telescope 63 3.3 Modern Telescopes 46 A Closer Look 3.1 A Night at Maunakea 65 3.3a Current Large Telescopes Around the World 46 3.8e The Major New Radio Projects 66 Figure It Out 3.1 Light-Gathering Power of a Telescope 47 4. Observing the Stars and Planets: Clockwork of the Figure It Out 3.2 Changing Units 47 Universe 75 3.3b The Next Generation of Optical and Infrared 4.1 The Phases of the Moon and Planets 76 Ground-Based Telescopes 51 4.2 Celestial Spectacles: Eclipses 77 3.4 The Big Picture: Mapping the Sky 52 Star Party 4.1 Observing Total Solar Eclipses 80

vii

viii Detailed Contents Credit: NASA The James Webb Space Telescope being tested.

4.2a Eerie Lunar Eclipses 81 5. Gravitation and Motion: The Early History of 4.2b Glorious Solar Eclipses 82 Astronomy 107 A Closer Look 4.1 Colors in the Sky 83 5.1 A Brief Survey of the Solar System 107 4.3 Twinkle, Twinkle, Little Star … 87 Star Party 5.1 Prograde and Retrograde Motions 108 4.4 The Concept of Apparent Magnitude 87 5.2 The Earth-Centered Astronomy of Ancient Greece 109 Figure It Out 4.1 Using the Magnitude Scale 88 A Closer Look 5.1 Ptolemaic Terms 110 4.5 Rising and Setting Stars 88 A Closer Look 5.2 The Antikythera Mechanism 111 A Closer Look 4.2 Photographing the Stars 89 5.3 A Heretical Idea: The Sun-Centered Universe 111 Figure It Out 4.2 Sidereal Time 90 Lives in Science 5.1 Copernicus 113 4.6 Celestial Coordinates to Label the Sky 91 5.4 The Keen Eyes of Tycho Brahe 114 4.7 The Reason for the Seasons 92 5.5 Johannes Kepler and His Laws of Orbits 114 Star Party 4.2 The Paths of the Moon and Planets 95 5.5a Kepler’s First Law 114 4.8 Time and the International Date Line 95 5.5b Kepler’s Second Law 114 4.9 Calendars 98 Lives in Science 5.2 Tycho Brahe 115 4.10 Keeping Time 100 A Closer Look 5.3 Kepler’s Laws 116 Lives in Science 5.3 Johannes Kepler 117

Detailed Contents ix Credit: Jay M. Pasachoff and the Chapin Library, Williams College A double page from Galileo’s Sidereus Nuncius (1610) showing his engravings of the face of the Moon as seen through his newfangled telescope.

5.5c Kepler’s Third Law 118 6. The Terrestrial Planets: Earth, Moon, and Their 5.6 The Demise of the Ptolemaic Model: Galileo Galilei 118 Relatives 133 5.7 On the Shoulders of Giants: Isaac Newton 119 6.1 Earth: There’s No Place Like Home 134 5.8 Clues to the Formation of Our Solar System 120 A Closer Look 6.1 Comparative Data for the Terrestrial Figure It Out 5.1 Kepler’s Third Law 121 Planets and Their Moons 134 Lives in Science 5.4 Galileo Galilei 121 6.1a Earth’s Interior 134 Star Party 5.2 Galileo’s Observations 124 A Closer Look 6.2 Density 136 A Closer Look 5.4 Newton’s Law of Universal 6.1b Continental Drift 138 Gravitation 124 6.1c Tides 139 Figure It Out 5.2 Newton’s Version of Kepler’s Third 6.1d Earth’s Atmosphere 139 Law 125 6.1e The Van Allen Belts 143 Lives in Science 5.5 Isaac Newton 126 6.2 The Moon 144 Figure It Out 5.3 Orbital Speed of Planets 127 6.2a The Moon’s Appearance 145

x Detailed Contents

A Closer Look 6.3 The First People on the Moon 145 6.2b The Lunar Surface 146 6.2c The Lunar Interior 151 6.2d The Origin of the Moon 152 6.2e Rocks from the Moon 153 6.3 Mercury 153 6.3a The Rotation of Mercury 154 6.3b Mercury’s History 155 6.3c Mercury Observed from Earth 155 A Closer Look 6.4 Naming the Features of Mercury 156 6.3d Spacecraft Views of Mercury 156 6.3e Mercury Research Rejuvenated 158 6.3f Mercury from MESSENGER 158 6.3g Continuing Exploration of Mercury 160 6.4 Venus 160 6.4a Transits of Venus 161 6.4b The Atmosphere of Venus 162 6.4c The Rotation of Venus 162 6.4d Why Is Venus So Incredibly Hot? 162 6.4e Spacecraft Observations of Venus’s Atmosphere 164 6.4f Radar Observations of Venus’s Surface 165 6.4g Venus Exploration in the Twenty-First Century 166 6.5 Mars 168 6.5a Characteristics of Mars 169

Credit: Jay M. Pasachoff 6.5b Mars’s Surface 169 Mae Jemison and Sally Ride, NASA astronauts, in a 2017 6.5c Mars’s Atmosphere 172 LEGO™ set, in front of a Space Shuttle. Credit: NASA/JPL-Caltech/Space Science Institute NASA’s Cassini mission farewell image of Saturn and its rings. The image is the last full mosaic taken two days before the spacecraft plunged into Saturn.

Detailed Contents xi

7.3a Uranus’s Atmosphere 210 7.3b Uranus’s Rings 211 7.3c Uranus’s Interior and Magnetic Field 212

e 7.4 Neptune 212 7.4a Neptune’s Atmosphere 213 7.4b Neptune’s Interior and Magnetic Field 215 7.4c Neptune’s Rings 216 A Closer Look 7.6 Naming the Rings of Neptune 216 7.4d Neptune’s Moon Triton 217 7.5 The Formation of the Giant Planets 218

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institut 8. Pluto, Comets, Asteroids, and Beyond 225 Terrain on Pluto, a close-up from NASA’s New Horizons. 8.1 Pluto 226 8.1a Pluto’s Mass and Size 226 8.1b Pluto’s Atmosphere 228 6.5d Mars’s Satellites 173 8.1c What Is Pluto? 228 A Closer Look 6.5 Mars Exploration Rovers, A Closer Look 8.1 Dwarf Planets 230 Mars Phoenix, and Mars Science Lab with 8.1d The Pluto System from New Horizons 230 Curiosity 174 8.1e Beyond Pluto 230 6.5e The Search for Life on Mars 177 8.2 Kuiper-Belt Objects and Dwarf Planets 232 6.5f Crewed Missions to Mars 180 8.3 Comets 235 8.3a The Composition of Comets 235 7. The Jovian Planets: Windswept Giants 189 8.3b The Origin and Evolution of Comets 236 7.1 Jupiter 190 8.3c Halley’s Comet 237 A Closer Look 7.1 Comparative Data for the Major 8.3d Comet Shoemaker–Levy 9 239 Worlds 190 8.3e Some Bright Comets 241 Star Party 7.1 Observing the Giant Planets 191 7.1a Spacecraft to Jupiter 191 Figure It Out 7.1 The Size of Jupiter 192 7.1b The Great Red Spot 192 7.1c Jupiter’s Atmosphere 193 7.1d Jupiter’s Interior 194 7.1e Jupiter’s Magnetic Field 194 7.1f Jupiter’s Ring 195 7.1g Jupiter’s Amazing Satellites 195 A Closer Look 7.2 Jupiter and Its Satellites in Mythology 200 7.1h JUICE at Jupiter 201 7.2 Saturn 201 7.2a Saturn’s Rings 201 7.2b Saturn’s Atmosphere 204 7.2c Saturn’s Interior and Magnetic Field 204 7.2d Saturn’s Moon Titan 204 A Closer Look 7.3 Saturn’s Satellites in Mythology 207 7.2e Saturn’s Other Satellites 207 A Closer Look 7.4 Saturn’s Rings and Moons from Cassini 208

7.3 Uranus 209 Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA A Closer Look 7.5 Uranus and Neptune in Asteroid and dwarf planet 1 Ceres, imaged from NASA’s Mythology 210 Dawn spacecraft that is orbiting it.

xii Detailed Contents

9.2g Future Observing Plans and Projects 275 9.3 The Nature of Exoplanet Systems 278 A Closer Look 9.1 Naming Stars, Exoplanets, and Kuiper-Belt-Objects 278 9.4 Goldilocks Planets 279 9.5 Brown Dwarfs 279 9.6 Planetary Systems in Formation 280

10. Our Star: The Sun 289 10.1 What Is the Sun’s Basic Structure? 290 10.1a The Photosphere 291 A Closer Look 10.1 The Most Common Elements in the Sun’s Photosphere 292 10.1b The Chromosphere 294 10.1c The Corona 295

Credit: NASA, ESA, and K. Sahu (STScI) 10.1d The Scientiﬁc Value of Eclipses 301 A white-dwarf star, Stein 2051 B, only 17 light-years from 10.2 Sunspots and Other Solar Activity 302 Earth, seen with the Hubble Space Telescope, with a more 10.2a What Are Those Blemishes on the Sun? 302 distant star appearing below it. The white dwarf passed Star Party 10.1 Observing Sunspots 303 in front of the other star, providing a successful test of 10.2b The Solar-Activity Cycle 303 Einstein’s general theory of relativity. 10.2c Fireworks on the Sun, and Space Weather 304 10.2d Filaments and Prominences 307 10.2e Decades Ahead of Solar Monitoring 307 10.3 The Sun and the Theory of Relativity 307 8.3f Spacecraft to Comets 243 Lives in Science 10.1 Albert Einstein 308 8.3g Rosetta Orbits Its Comet 244 8.4 Meteoroids 244 8.4a Types and Sizes of Meteorites 244 8.4b Meteor Showers 247 A Closer Look 8.2 Meteor Showers 248 Star Party 8.1 Observing a Meteor Shower 248 8.5 Asteroids 249 8.5a General Properties of Asteroids 249 A Closer Look 8.3 The Extinction of the Dinosaurs 249 8.5b Asteroids Viewed Close-Up 250 8.5c Near-Earth Objects 254 8.5d Interstellar Visitor 256 8.5e Future Asteroid Missions 256

9. Our Solar System and Others 263 9.1 The Formation of the Solar System 264 9.1a Collapse of a Cloud 264 9.1b Models of Planet Formation 265

9.2 Extrasolar Planets (Exoplanets) 266 Credit: NASA, ESA, and A. Angelich (NRAO/AUI/NSF) Hubble credit: NASA, ESA, and R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon Betty Moore Foundation) Chandra credit: NASA/CXC/Penn State/K. Frank et al. ALMA credit: (ESO/NAOJ/NRAO) and R. Indebetouw (NRAO/AUI/NSF) 9.2a Astrometric Method 267 A multiwavelength view of Supernova 1987A, with 9.2b Timing of Radio Pulsars 267 green showing Hubble views of how the expanding 9.2c Periodic Doppler Shifts: The Doppler-Wobble shock wave from the star that exploded is colliding Method 267 with material ejected previously, and the red showing 9.2d Transiting Planets: The Blink Method 269 dust imaged with the ALMA millimeter/submillimeter 9.2e Direct Imaging of Exoplanets 272 array. Blue is hot gas imaged with the Chandra X-ray 9.2f Gravitational Microlensing 275 Observatory.

Detailed Contents xiii

11.8 Clusters of Stars 343 11.8a Open and Globular Star Clusters 343 A Closer Look 11.4 Star Clusters in Our Galaxy 344 11.8b How Old Are Star Clusters? 345 11.8c Gaia’s Hertzsprung–Russell Diagram 346 A Closer Look 11.5 How We Measure Basic Stellar Parameters 348

12. How the Stars Shine: Cosmic Furnaces 357 12.1 Star Birth 358 12.1a Collapse of a Cloud 358 12.1b The Birth Cries of Stars 362 12.2 Where Stars Get Their Energy 364 12.3 Atoms and Nuclei 365 12.3a Subatomic Particles 365 12.3b Isotopes 365 Figure It Out 12.1 Energy Generation in the Sun 366 12.3c Radioactivity and Neutrinos 367 Credit: NASA, ESA, and P. Crowther (University of Sheffield) 12.4 Stars Shining Brightly 367 Star cluster R136 in the Tarantula Nebula in the Large 12.5 Why Stars Shine 368 Magellanic Cloud, imaged with Hubble. 12.6 Brown Dwarfs 368 12.7 The Solar Neutrino Experiment 370 11. Stars: Distant Suns 317 12.7a Initial Measurements 370 11.1 Colors, Temperatures, and Spectra of Stars 318 12.7b Further Solar Neutrino Experiments 371 11.1a Taking a Star’s Temperature 318 12.7c Beyond Solar Neutrinos 372 11.1b How Do We Classify Stars? 319 12.8 The End States of Stars 374 11.1c The Coolest Stars 320 11.2 How Distant Are the Stars? 320 Figure It Out 11.1 Stellar Triangulation 323 11.3 How Powerful Are the Stars? 323 A Closer Look 11.1 Using Absolute Magnitudes 325 11.4 Temperature–Luminosity Diagrams 325 Figure It Out 11.2 The Inverse-Square Law 326 11.5 How Do Stars Move? 328 11.5a Proper Motions of Stars 328 Figure It Out 11.3 A Star’s Luminosity 329 11.5b Radial Velocities of Stars 329 A Closer Look 11.2 Proxima Centauri: The Nearest Star Beyond the Sun 331 11.6 “Social Stars”: Binaries 332 Figure It Out 11.4 Doppler Shifts 333 11.6a Pairs of Stars and Their Uses 333 Figure It Out 11.5 Binary Stars 335 11.6b How Do We Weigh Stars? 337 11.6c The Mass–Luminosity Relation 337 A Closer Look 11.3 A Sense of Mass: Weighing

Stars 338 Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Figure It Out 11.6 The Mass–Luminosity The Bubble Nebula, NGC 7635, gas expanding around a Relation 339 massive star. The object is 7 light-years across, and is imaged 11.7 Stars That Don’t Shine Steadily 339 here with Hubble.

xiv Detailed Contents

13.3e Slowing Pulsars and Fast Pulsars 406 13.3f Binary Pulsars and Gravitational Waves 406 13.3g A Pulsar with a Planet 408 13.3h X-ray Binaries 408

14. Black Holes: The End of Space and Time 415 14.1 The Formation of a Stellar-Mass Black Hole 416 14.2 The Photon Sphere 416 14.3 The Event Horizon 417 14.3a A Newtonian Argument 417 14.3b Black Holes in General Relativity 418 14.4 Time Dilation 419 14.5 Properties of Black Holes 419 14.5a Rotating Black Holes 419 14.5b Measuring Black-Hole Spin 420 14.6 Passageways to Distant Lands? 422 14.7 Detecting a Black Hole 422 14.7a Hot Accretion Disks 422 14.7b Cygnus X-1: The First Plausible Stellar-Mass Black Hole 423 14.7c Other Black-Hole Candidates 424 Figure It Out 14.1 Binary Stars and Kepler’s Third Law 424 Credit: NASA, ESA, and M. Mutchler (STScI) A pair of spiral galaxies, NGC 4302 and 4298, both about 55 million light-years away and imaged with the Hubble Space Telescope.

13. The Death of Stars: Recycling 381 13.1 The Death of the Sun 381 13.1a Red Giants 381 13.1b Planetary Nebulae 383 13.1c White Dwarfs 384 13.1d Summary of the Sun’s Evolution 386 13.1e Binary Stars and Novae 387 13.2 Supernovae: Stellar Fireworks! 388 13.2a Core-Collapse Supernovae 389 13.2b White-Dwarf Supernovae (Type Ia) 391 13.2c Superluminous Supernovae 393 13.2d Observing Supernovae 393 13.2e Supernova Remnants 393 A Closer Look 13.1 Searching for Supernovae 395 13.2f Supernovae and Us 396 13.2g Supernova 1987A! 397

13.2h Cosmic Rays 401 Credit: NASA, ESA, and M. Brodwin (University of Missouri) 13.3 Pulsars: Stellar Beacons 402 A cluster of galaxies 10 billion light-years from Earth, with 13.3a Neutron Stars 402 500 trillion times the mass of our Sun. Hot gas in the middle, 13.3b The Discovery of Pulsars 402 imaged with the Chandra X-ray Observatory, shows as blue- 13.3c What Are Pulsars? 403 white overlaying Hubble’s visible-light image in green and 13.3d The Crab, Pulsars, and Supernovae 404 the Spitzer Space Telescope’s image in red.

Detailed Contents xv Credit: European Space Agency/Planck Consortium An all-sky map made with the European Space Agency’s Planck spacecraft, which was also used to map the cosmic background radiation. The image is a composite of magnetic-ﬁeld, atomic “free-free,” dust, and carbon-monoxide components.

14.7d The Strange Case of SS433 425 16. A Universe of Galaxies 479 14.8 Supermassive Black Holes 426 16.1 The Discovery of Galaxies 480 14.9 Moderation in All Things 428 16.1a The Shapley–Curtis Debate 480 14.10 Gamma-ray Bursts: Birth Cries of Black Holes? 430 16.1b Galaxies: “Island Universes” 482 14.10a How Far Away Are Gamma-ray Bursts? 430 16.2 Types of Galaxies 483 14.10b Models of Gamma-ray Bursts 431 16.2a Spiral Galaxies 483 14.11 Mini Black Holes 433 16.2b Elliptical Galaxies 485 14.12 The Detection of Gravitational Waves 433 16.2c Other Galaxy Types 486 Proposal: The Maxwell–Einstein speed 440 16.3 Habitats of Galaxies 488 16.3a Clusters of Galaxies 488 15. The Milky Way: Our Home in the Universe 447 Star Party 16.1 Observing Galaxies 488 15.1 Our Galaxy: The Milky Way 448 16.3b Superclusters of Galaxies 491 Star Party 15.1 Observing the Milky Way 448 16.4 The Dark Side of Matter 491 15.2 The Illusion That We Are at the Center 450 16.4a The Rotation Curve of the Milky Way 15.3 Nebulae: Interstellar Clouds 451 Galaxy 491 15.4 The Parts of Our Galaxy 453 16.4b Dark Matter Everywhere 493 15.5 The Center of Our Galaxy 456 Figure It Out 16.1 Calculating the Mass from 15.6 All-Sky Maps of Our Galaxy 460 the Rotation Curve 494 15.7 Our Pinwheel Galaxy 461 16.4c What Is Dark Matter? 495 15.8 Why Does Our Galaxy Have Spiral Arms? 463 16.5 Gravitational Lensing 497 15.9 Matter Between the Stars 464 16.6 The Birth and Life of Galaxies 503 15.10 Radio Observations of Our Galaxy 465 16.7 The Expanding Universe 503 15.11 Mapping Our Galaxy 466 Figure It Out 16.2 Redshifts and the Hubble–Lemaî tre 15.12 Radio Spectral Lines from Molecules 468 Law 505 15.13 The Formation of Stars 468 Figure It Out 16.3 Using the Hubble–Lemaî tre Law to 15.14 At a Radio Observatory 471 Determine Distances 506

xvi Detailed Contents NASA , ESA, and B. Salmon (STScI)

A gravitationally lensed embryonic galaxy, only half a billion years after the big bang. It is only 1% the mass of our Milky Way Galaxy, and is revealing an early stage of galaxy formation. The lensing smeared it into an arc; other galaxies about that far away and far back in time appear only as reddish dots. The image was taken with the Hubble Space Telescope.

16.8 The Search for the Most Distant Galaxies 506 18.2a The Hubble-Lemaître Law 555 Figure It Out 16.4 Relativistic Effects 508 18.2b Expansion Without a Center 556 16.9 The Evolution of Galaxies 511 18.2c What Is Actually Expanding? 558 16.10 Evolution of Large-Scale Structure 514 18.3 The Age of the Universe 559 18.3a Finding Out How Old 559 17. Quasars and Active Galaxies 523 Figure It Out 18.1 The Hubble Time 560 17.1 Active Galactic Nuclei 524 18.3b The Quest for Hubble’s Constant 560 17.2 Quasars: Denizens of the Distant Past 526 18.3c A Key Project of the Hubble Space 17.2a The Discovery of Quasars 526 Telescope 562 17.2b Puzzling Spectra 527 18.3d Deviations from Uniform Expansion 566 17.2c The Nature of the Redshift 528 18.3e Type Ia Supernovae as Cosmological 17.3 How Are Quasars Powered? 529 Yardsticks 566 17.3a A Big Punch from a Tiny Volume 531 18.4 The Geometry and Fate of the Universe 567 17.3b What Is the Energy Source? 531 18.4a The Cosmological Principle: Uniformity 567 17.3c Accretion Disks and Jets 532 18.4b No “Cosmological Constant”? 567 17.4 What Are Quasars? 533 18.4c Three Kinds of Possible Universes 569 17.5 Are We Being Fooled? 536 Figure It Out 18.2 The Critical Density and

17.6 Finding Supermassive Black Holes 537 ΩM 569 Figure It Out 17.1 The Central Mass in a Galaxy 538 A Closer Look 18.1 Finite Flat and Hyperbolic 17.7 The Effects of Beaming 540 Universes 571 17.8 Probes of the Universe 543 18.4d Two-Dimensional Analogues 572 18.4e What Kind of Universe Do We Live In? 573 18. Cosmology: The Birth and Life of the Cosmos 553 18.4f Obstacles Along the Way 574 18.1 Olbers’s Paradox 554 18.5 Measuring the Expected Deceleration 574 18.2 An Expanding Universe 555 18.5a The High-Redshift Hubble Diagram 574

Detailed Contents xvii

19.3g Ground-Based Telescopes for the Cosmic Background Radiation 599 19.3h Polarization of the Cosmic Background Radiation 599 19.4 The Early Universe 600 19.4a Going Back in Time 600 19.4b A Brief History of the Early Universe 602 19.4c Primordial Nucleosynthesis 604 19.5 The Inflationary Universe 606 19.5a Problems with the Original Big-Bang Model 606 19.5b Inflation to the Rescue 607 Figure It Out 19.1 Inflation of the Early Universe 609 19.5c Forces in the Universe 609 19.5d Supercooling the Universe 612 19.5e Successes of Inflation 612 19.5f The Ultimate Free Lunch? 613 Figure It Out 19.2 Virtual Particles 614 19.6 A Universe of Universes 614 19.7 A Universe Finely Tuned for Life? 616

20. Life in the Universe 623 20.1 The Origin of Life 624 20.2 Life in the Solar System 626 20.3 Suitable Stars for Intelligent Life 626 Credit: Jay M. Pasachoff 20.4 The Search for Extraterrestrial Intelligence 627 A balloon alien, as yet unknown in reality. Figure It Out 20.1 Interstellar Travel and Einstein’s Relativity 628 18.5b Type Ia (White-Dwarf) Supernovae 575 20.5 Communicating with Extraterrestrials 632 18.5c An Accelerating Universe! 575 20.6 The Statistics of Intelligent Extraterrestrial Life 633 18.5d Einstein’s Biggest Blunder? 577 20.6a The Drake Equation 633 18.5e Dark Energy 578 20.6b Where Is Everyone? 635 18.5f The Cosmic Jerk 579 Figure It Out 20.2 The Drake Equation 636 18.6 The Future of the Universe 581 20.7 UFOs and the Scientiﬁc Method 637 20.7a UFOs 637 19. In the Beginning 589 20.7b Of Truth and Theories 639 19.1 The Steady-State Theory 590 20.8 Conclusion 639 19.2 The Cosmic Microwave Background Radiation 591 Epilogue 644 19.2a A Faint Hiss from All Directions 591 19.2b Origin of the Microwave Radiation 592 Appendix 1/2. Measurement Systems/Basic Constants 645 19.3 Deviations from Isotropy 594 Appendix 3. Planets and Dwarf Planets 647 19.3a Ripples in the Cosmic Microwave Appendix 4. The Brightest Stars 649 Background 594 Appendix 5. The Nearest Stars 651 19.3b The Overall Geometry of the Universe 595 Appendix 6. The Messier Catalogue 654 19.3c The Wilkinson Microwave Anisotropy Probe Appendix 7. The Constellations 656 (WMAP) 596 Appendix 8. Star Names 658 19.3d The Planck Spacecraft 596 19.3e Evaluating the Cosmic Background Selected reading 661 Radiation 596 Glossary 668 19.3f Planck Maps Objects in Space 599 Index 685

© in this web service Cambridge University Press www.cambridge.org Cambridge University Press 978-1-108-43138-5 — The Cosmos 5th Edition Frontmatter More Information NASA, ESA, and STScI NASA, ESA, and STScI

Saturn and Mars at their closest places to Earth as they orbit, the oppositions of 2018, imaged with the Hubble Space Telescope. Saturn’s northern-hemisphere summer triggered a large storm, seen here as it disintegrates near Saturn’s north pole. Mars’s southern-hemisphere spring triggered a huge dust storm that eventually covered the whole planet.

Preface

Astronomy continues to flourish, with huge discoveries such as the and the Daniel K. Inouye Solar Telescope in Hawaii for detailed one that pairs of giant black holes merge, sending ripples through studies of the Sun. The Hubble Space Telescope, with its latest space-time – so-called gravitational waves – that we can pick up on updated set of cameras, sends down exciting data all the time, and Earth. Even the merger of a pair of neutron stars has been detected we anticipate the launch in 2019 of the James Webb Space Telescope not only from the gravitational waves – let’s say by ear, given the with its mirror much larger than Hubble’s. The latest space obser- “chirp” of detection – but also with ordinary telescopes, the eyes of vatories transmit images made with gamma rays, with x-rays, and the Universe. So, as of 2018, we have the eyes and the ears of the with infrared radiation. The overall structure of the Universe is Universe working together. being mapped and analyzed, with catalogues of millions of objects being compiled. Cosmology has become an observationally rich science. In Solar System studies, NASA’s Curiosity rover triumphantly travels around Mars, bearing instruments to investigate Mars’s past habitability. The Cassini spacecraft that orbited Saturn for 13 years plunged into its surface in 2017, to protect Saturn’s moons from being contaminated with terrestrial microbes. Spacecraft recently orbited the asteroid and dwarf planet Ceres and a comet. Another spacecraft flew right by Pluto and its moons and is now en route to a tiny object beyond them. Moreover, new electronic instruments and computer capabilities, new space missions to Solar-System objects, and advances in computational astronomy and in theoretical work will continue to bring forth exciting results. In this latest edition of The Cosmos: Astronomy in the New Millennium, we describe the current state of astronomy, both the fundamentals of astronomical knowledge that have been built up over decades and the incredible advances that are now taking place. We want simply to share with students the excitement and magnifi- cence of the Universe. We try to cover all branches of astronomy without slighting any of them; each teacher and each student may well find special inter- NASA/JPL-Caltech/Space Science Institute ests that are different from our own. One of our aims in writing this The dot between two of Saturn’s rings is Earth, our planet. NASA’s book is to educate citizens in the hope that they will understand the Cassini spacecraft orbited in the Saturn system through 2017, value and methods of scientific research in general and astronomical when it was directed to plunge into Saturn’s atmosphere to safely research in particular. destroy it without risking contaminating any of Saturn’s moons In writing this book, we share the goals of a commission of the with terrestrial life-forms. Association of American Colleges, whose report on the college cur- riculum stated: The Universe’s expansion – which was long thought to be slowing down – is, astonishingly, accelerating, presumably as a conse- A person who understands what science is recognizes that scientific concepts are created by acts of human intelligence and imagination; quence of mysterious “dark energy.” We have discovered thousands comprehends the distinction between observation and inference and of planets around other stars – other solar systems abound! A gen- between the occasional role of accidental discovery in scientific inves- eration of large optical telescopes has been built on mountaintops, tigation and the deliberate strategy of forming and testing hypoth- and arrays of dozens of radio telescopes such as the Atacama Large eses; understands how theories are formed, tested, validated, and Millimeter/submillimeter Array (ALMA) at an extremely high-alti- accorded provisional acceptance; and discriminates between conclu- tude site explore their part of the spectrum at high resolution. Still sions that rest on unverified assertion and those that are developed larger telescopes are being planned or built, including the Thirty from the application of scientific reasoning. Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope, all for optical and near-infrared studies, The scientific method permeates the book.

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What is science? The following statement was originally drafted Anyone choosing an astronomy textbook should consider the by the Panel on Public Affairs of the American Physical Society, in following: an attempt to meet the perceived need for a very short statement •฀ Readability. Our prose is extremely clear and readable. that would differentiate science from pseudoscience. This state- •฀ Scientific accuracy. Our book is written by experts in the field and ment has been endorsed as a proposal to other scientific societies has the various chapters checked by other experts. by the Council of the American Physical Society, and was endorsed •฀ Up to date. Our book has sunspot numbers up to date to show the by the Executive Board of the American Association of Physics current phase of the sunspot cycle; exoplanet lists and diagrams up Teachers: to the current situation; the latest on the Cassini mission to Saturn and to Curiosity roaming around on Mars; images of the corona Science is the systematic enterprise of gathering knowledge about the at the 2017 total solar eclipse; a discussion of the Hubble constant world and organizing and condensing that knowledge into testable and the expansion of the Universe, with slightly different values laws and theories. The success and credibility of science is anchored coming from an overall measurement of the cosmic background in the willingness of scientists to: radiation from the Planck spacecraft compared with the latest val- Expose their ideas and results to independent testing and replica- ues of the Universe’s expansion and acceleration from supernova tion by other scientists; this requires the complete and open exchange observations; and more. of data, procedures, and materials; Abandon or modify accepted conclusions when confronted with •฀ Features like A Closer Look, Figure It Out, and Star Party that help more complete or reliable experimental evidence. Adherence to these this book be useful for astronomy survey courses of one semester principles provides a mechanism for self-correction that is the foun- or of those that spread the material out over two or more semesters. dation of the credibility of science. NEW IN THIS EDITION Our book, through the methods it describes, should reveal this sys- •฀ Updated data (such as sunspot numbers showing the current min- tematic enterprise of science to the readers. imum of the sunspot cycle) and figures throughout the text, as well Because one cannot adequately cover the whole Universe in a few as new images from recent space missions (such as the Cassini mis- months, or even a year, we have had to pick and choose topics from sion to Saturn as well as Curiosity roaming around on Mars) and within the various branches of astronomy, while trying to describe a ground-based telescopes (such as images of the corona at the 2017 wide range, to convey the spirit of contemporary astronomy and of total solar eclipse). the scientists working in it. Our mix includes much basic astronomy •฀ Expanded discussions of the hottest current topics, such as New and many of the exciting topics now at the forefront. Horizons’ flyby of Pluto (Chapter 8), the latest on exoplanets Two examples are the currently hottest topics in astronomy: the (Chapter 9) and dark matter (Chapter 18), and the direct detection discovery of thousands of planets around other stars (so-called ex- of gravitational waves by LIGO (Chapter 14). oplanets) and the discovery of gravitational waves from merging •฀ The latest discoveries on supernovae, including pictures of the first black holes and neutron stars. Our exoplanet coverage brings the known strongly gravitationally lensed supernova (showing five discoveries and the new techniques and spacecrat being used up separate images of that supernova). to 2018, with a graph of the Kepler spacecrat’s discoveries, men- •฀ New observations of the 4-million-solar-mass black hole at the tion of the K2 version of the spacecrat including an image with its center of our Milky Way Galaxy. ields of view overlain, and a discussion of new instruments, such •฀ The latest progress on precision measurement of the Hubble con- as NASA’s Transiting Exoplanet Survey Satellite (TESS), launched stant for the expansion of the Universe. in 2018. •฀ Additional end-of-chapter questions and updated summaries and For the fantastic discovery of gravitational waves from collisions of glossary. black holes over a billion light-years away, which was honored with the 2017 Nobel Prize in Physics, we have expanded our previous cov- ORGANIZATION erage of the Laser Interferometer Gravitational-wave Observatory The fifth edition of The Cosmos: Astronomy in the New Millennium is (LIGO). We include the latest update to the graph of spiraling neu- generally organized in an Earth-outward approach. Chapter 1 gives tron stars that led to an indirect veriication of the existence of grav- an overview of the Universe. Chapter 2 presents fundamental astro- itational waves, which was recognized with the 1993 Nobel Prize in nomical concepts about light, matter, and energy, while Chapter 3 Physics. Moreover, we discuss LIGO’s August 2017 detection of two summarizes the various types of telescopes used to explore the such neutron stars merging, and the result not only of the gravita- electromagnetic spectrum. In Chapter 4, we discuss easily observed tional waves themselves but also of concomitant gamma rays, visible astronomical phenomena and the celestial sphere. Some professors light, and other forms of electromagnetic waves. prefer to cover that material at the very beginning of the course or at For the 2017 total solar eclipse whose path crossed the United other points, and there is no problem with doing so. States, we have the latest imaging and a discussion of why such ob- Chapter 5 examines the early history of the study of astronomy. servations were scientiically important. Chapters 6 through 8 cover the Solar System and its occupants,

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although a thorough discussion of the Sun is reserved for later, in FEATURES Chapter 10. Chapter 6 compares Earth to the Moon and Earth’s The Cosmos: Astronomy in the New Millennium offers instructors a nearest planetary neighbors, Venus and Mars. Based largely on the concise overview of a wide range of astronomical topics. An early Voyager, Galileo, and Cassini data, Chapter 7 compares and contrasts discussion of the scientific method stresses its importance in the ver- the Jovian gas/liquid giants – Jupiter, Saturn, Uranus, and Neptune. ification of observations. The text presents up-to-date coverage of Chapter 8 looks at the outermost part of the Solar System, including many important findings and theories as well as the latest images, Pluto and its moon, Charon, as well as other Kuiper-belt objects still including observations of Jupiter and Saturn from the Cassini– farther out; the chapter also spotlights comets and meteoroids, the Huygens mission (including the landing on Titan), close-up obser- Solar System’s vagabonds. Chapter 9 discusses the formation of our vations of Mars, images of stars in formation and of gas near them own Solar System and describes the exciting discovery of thousands from the largest telescopes in space, and coverage of recent total of exoplanets and exoplanet candidates around other stars. solar eclipses and of the pair of transits of Venus – the like of which Chapter 10 concentrates on the Sun, our nearest star, exploring will not be seen on Earth until the year 2117, in the twenty-second its various components and the solar activity cycle. Moving out- century. ward, Chapters 11 through 14 examine all aspects of stars. Chapter We provide, as well, a sampling of the many significant find- 11 begins by presenting observational traits of stars – their colors ings from the Hubble Space Telescope. Numerous images from the and types – and goes on to show how we measure their distances, Chandra X-ray Observatory, the Spitzer Space Telescope, the Planck brightnesses, and motions. It also discusses binary stars, variable spacecraft that studied the cosmic background radiation, and the stars, and star clusters, in the process showing how we derive stellar Gaia spacecraft that is mapping a billion of the nearest stars, also masses and ages. Chapter 12 answers the question of how stars shine appear, as do results from the Swift spacecraft that is monitoring and reveals that all stars have life cycles. Chapter 13 tells what hap- gamma-ray bursts, among the most powerful and violent phenom- pens when stars die and describes some of the peculiar objects that ena in the Universe (the origin of one type of which is now proven violent stellar death can create, including neutron stars and pulsars. by observations of the merging neutron stars). Of particular interest Black holes, the most bizarre objects to result from star death, are the is the recent advance in our understanding of the age and expansion focus of Chapter 14. We end the chapter by describing how the Laser of the Universe, both through better measurements of the current Interferometer Gravitational-wave Observatory (LIGO) detected, expansion rate and through the discovery that the Universe’s expan- several times, the tiniest possible variation in the length of a light sion is now speeding up with time. We also present the recent excit- beam, with the waves interpreted as coming from the merger of two ing measurements that allow astronomers to determine the overall black holes each containing 10−30 times as much mass as the Sun. geometry of the Universe and the early appearance of large-scale And in August 2017, LIGO even detected the merger of two neutron structure through detailed observations of the cosmic background stars simultaneously with telescopes around the world and in space radiation. seeing the event in ordinary, electromagnetic radiation. We are in the era of “Multi-Messenger Astronomy,” as NASA has recently put it: PEDAGOGY “photons, gravitational waves, and particle astrophysics.” 1. Chapter฀opener. Each chapter includes the following features: As we explore further, Chapter 15 describes the parts of the Milky •฀ Origins. NASA has chosen Origins as one of its major themes Way Galaxy and our place in it. Chapter 16 pushes beyond the Milky for the organization of its missions and has several spacecraft Way to discuss galaxies in general, the fundamental units of the in the Origins program. Inspired by this choice, each chapter Universe, and evidence that they consist largely of dark matter. Ways piques the reader’s interest with some of the discoveries, tools, in which we are studying the evolution of galaxies are also described. and theories behind our effort to understand the Universe and Chapter 17 looks at quasars, distant and powerful objects that shine its relationship to us. because gigantic black holes are swallowing gas in the central regions •฀ Chapter introduction, summarizing the main topics discussed of galaxies. in each chapter and how these fit into the rest of the book. Chapters 18 and 19 consider the ultimate questions of cosmo- •฀ Aims, setting out what students should expect to learn from logical creation by analyzing recent findings and current theories. the material that follows. Evidence that the expansion of the Universe is currently speeding 2. ฀Star฀Parties. An occasional feature that shows students how to up with time (probably propelled by a mysterious “dark energy”), find things in the sky. These include observing exercises and links possibilities for the overall geometry and fate of the Universe, rip- to the star maps that appear on the inside covers of the book. For ples in the cosmic background radiation, the origin and early expo- example, Star Party 5.1 explains how to sketch the position of nential growth of the Universe, and the idea of multiple universes Mars or Jupiter in relation to the stars near them, repeating this are among the fascinating (and sometimes very speculative) topics exercise every 6–9 days over the course of 2–3 months. Students explored. Lastly, Chapter 20 discusses the always-intriguing search examine their results to see the planets in their prograde and ret- for extraterrestrial intelligence. rograde motions, which are important to understand in order to

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properly comprehend the work of Copernicus and how it super- (together with the authors’ personal website http://www.solarcorona seded the model of Ptolemy. .net) is regularly updated to include the latest discoveries and photo- 3. ฀Figure฀It฀Out. In some astronomy courses, it may be appropri- graphs from various sources. It features the following: ate to elaborate on equations. Because we wrote The Cosmos: •฀ Multiple-choice self-tests and other useful information such as lists Astronomy in the New Millennium to be a descriptive presenta- of typographical errors, updates to various new scientific discov- tion of modern astronomy for liberal-arts students, we kept eries since the publication of the textbook, and links to websites the use of mathematics to a minimum. However, we recognize such as those with new discoveries as yet unknown at the time of that some instructors wish to introduce their students to more this printing. of the mathematics associated with astronomical phenomena. •฀ “Misconceptions.” Recent educational research has shown that stu- Consequently, we provide mathematical features, numbered so dents often need to unlearn incorrect ideas in order to understand they can be assigned or not, at the instructor’s option. Figure It the correct ones. A list of these misconceptions – as well as the Out 5.1, for example, gives a mathematical treatment of Kepler’s correct alternatives – is available on our website. third law that can be included in a course in a way that is easy to •฀ Links to relevant websites on a wide variety of astronomical mate- mark on a syllabus; similarly, Figure It Out 5.2 gives professors the rial, such as http://photojournal.jpl.nasa.gov for planetary images; option of introducing Newton’s formulation of Kepler’s third law http://sidc.oma.be/silso for the latest sunspot cycle plots; http:// to find masses. spaceweather.com for the latest on daily sunspots or auroras; 4. ฀Lives฀in฀Science. These boxes provide biographies of important and http://hubblesite.org for a wide range of new Hubble Space historical figures like 5.1 Copernicus, 5.2 Tycho, 5.3 Kepler, 5.4 Telescope observations. Galileo, and 5.5 Newton. Lives in Science 10.1 discusses Albert •฀ People in Astronomy. A series of interviews presenting a famous Einstein. contemporary astronomer engaged in conversation about a 5. ฀A฀Closer฀Look. Using these boxes, students can further explore variety of topics, such as: current and future work in astron- interesting topics, such as size scales in the Universe, observing omy, what led that person to study and pursue astronomy as with large telescopes, various celestial phenomena, mythology, a career, and why learning about astronomy is an important and naming systems. For example, we are pleased to supply some scientific and human endeavor. We interviewed a diverse set exciting new close-up views of Mars from NASA’s Curiosity rover of astronomers – diverse both personally and in astronomical that is now on its surface in A Closer Look 6.5, whereas in A Closer field of study. We discussed Saturn with Carolyn Porco, the Look 5.1 we specifically define the main features of the Ptolemaic head of the Saturn imaging team on the Cassini spacecraft; system: deferent, epicycle, and equant. brown dwarfs and exoplanet astronomy with Gibor Basri and 6. ฀Key฀words฀and฀glossary. New vocabulary is boldfaced in the text how he got interested in astronomy; space astronomy with Jeff and in the expanded summaries that are given at the end of each Hoffman, a former astronaut who helped upgrade the Hubble chapter, and defined in the glossary. Space Telescope in orbit; and Sandra Faber about galaxies. We 7. ฀Chapter฀summary. Each chapter includes the following features: hope that students enjoy reading their comments as much as •฀ Concept Review, summarizing the main topics discussed. we enjoyed speaking with them and learning about their varied •฀ Questions. An expanded set of end-of-chapter questions cov- interests and backgrounds. ers a range of material and includes some that are straight- forward to answer from the text and others that require more STAR CHARTS thought. Pasachoff’s Peterson Field Guide to the Stars and Planets is a suggested •฀ Topics for Discussion. A list of themes and questions aimed at accompaniment for those wanting monthly star maps, star charts, engaging students in deeper explorations of the material dis- and other detailed observing aids; see http://www.solarcorona.com. cussed in each chapter. Quarterly star maps, improved and redrawn for us for The Cosmos: 8. ฀Appendices฀for฀additional฀coverage. Appendices at the end of Astronomy for the New Millennium by the foremost celestial cartog- the book provide additional information on planets, stars, con- rapher, Wil Tirion of The Netherlands, appear on the inside covers stellations, and nonstellar objects. in The Cosmos, 5th edition. 9. ฀Sky฀Maps. Inside the covers of the book, students will find the exceptionally beautiful sky maps by Wil Tirion to help them find ACKNOWLEDGMENTS their way around the sky when they go outside to observe the The publishers join us in placing a heavy premium on accuracy, and stars. we have made certain that the manuscript and past editions have been carefully read and considered. As a result, students will find that ONLINE RESOURCES the statements in this book, brief as they are, are authoritative. Adopters of The Cosmos, 5th edition, can access a rich array of teach- This fifth edition of The Cosmos benefited from new and updated ing and learning resources at http://thecosmos5.com. The website photographs and comments on text from Seth Shostak (SETI Institute)

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on SETI, Daniel Wertheimer (University of California, Berkeley) on (Georgia State U.), CHARA; Howard Bond (Penn State and STScl), SETI, Lynn Cominsky (Sonoma State University) on gamma-ray astron- V838 Cygni; Lorenzo Reynard (South African Radio Astronomy omy, Leon Golub (Harvard-Smithsonian Center for Astrophysics) on Observatory), Square Kilometer Array; Marek Demianski (Williams heliophysics, Joel Weisberg (Carleton College) on gravitational waves College and University of Warsaw), supernovae and cosmology; from the double pulsar, Richard Manchester (CSIRO, Australia) on Alan Stern and Cathy Olkin (SwRI), Dale Cruikshank (NASA Ames), pulsars, Rosemary Killen (NASA’s Goddard Space Flight Center) Rick Binzel (MIT), Bill McKinnon (Washington U.), Pluto; and and Carl Schmidt (University of Virginia) on Mercury, Augustin Eric Mamajek (NASA’s JPL-Caltech), planetary and stellar data and Sanchez Lavega (Valencia) on the winds of Jupiter and Saturn, Laura names. Brenneman (Harvard-Smithsonian Center for Astrophysics) on future For her extensive editorial consulting, we thank Madeline Kennedy x-ray missions, Alan Guth (MIT) and Adrienne Erickcek (University in Williamstown. For additional assistance, we thank Michele Rech of North Carolina) on the inflationary universe, and Eric Nash in Williamstown. (NASA’s Goddard Space Flight Center) on the ozone hole. We also At Cambridge University Press, we thank our commissioning thank William Graham for useful comments. The fourth edition of editor Vince Higgs, and Ilaria Tassistro and her editorial team, as well The Cosmos benefited from the advice and special images provided as Charlie Howell and his production team. by Lynn Cominsky (Sonoma State University), Leon Golub (Harvard- J.M.P. thanks various members of his family, who have pro- Smithsonian Center for Astrophysics), Joel Weisberg (Carleton vided vital and valuable editorial services in addition to their gen- College), Daniel Seaton (Royal Observatory of Belgium), John Johnson eral support. His wife, Naomi, has always been very helpful both (Harvard-Smithsonian Center for Astrophysics), Robert Simmon personally and editorially. He is grateful for the family support of (NASA’s Goddard Space Flight Center), Richard McCray (University of Deborah Pasachoff/Ian Kezsbom/Lily Kezsbom/Jacob Kezsbom/ Colorado), Richard Manchester (CSIRO, Australia), Daniel Stern (Jet Xander Kezsbom and of Eloise Pasachoff/Tom Glaisyer/Samuel Propulsion Laboratory), Daniel Mortlock (Imperial College, London), Glaisyer/Jessica Glaisyer. Matthew Templeton and Arne Hernden (AAVSO), Stefan Fichtel A.F. thanks his children, Zoe, Simon, Caprielle, and Orion (Ixtract), Federica Bianco (Las Cumbres Observatory Global Telescope Filippenko, for the long hours they endured while he was busy work- Network and the University of California, Santa Barbara), Gareth ing on this book rather than spending time with them; they mean Williams (Harvard-Smithsonian Center for Astrophysics), Lorne the universe to him. A.F. also thanks his wife, Noelle Filippenko, for McKee (National Resources Canada), Jens Vellev (Aarhus University), her incredible patience, advice, and support; he could not have suc- Gerard van Belle (Lowell Observatory), Geoff Marcy (University of ceeded without her, and he looks forward to sharing more of the California, Berkeley), Wayne Hammond (Chapin Library of Williams wonders of the cosmos with her. College), and Axel Mellinger (Central Michigan University). We are extremely grateful to all the individuals named above for At the time of proof for the fifth edition, we benefitted from their assistance. Of course, it is we who have put this all together, additional consultations with Gerald Williger (U. Louisville; cur- and we alone are responsible for the content. We would appreciate rently a Fulbright Scholar at Konkoly Observatory) on the full hearing from readers with suggestions for improved presentation set of chapters; Mark Showalter (SETI Institute), Jupiter’s moons; of topics, with comments about specific points that need clarifi- Carolyn Porco (Southwest Research Institute), Cassini/Saturn; cation, with typographical or other errors, or just to tell us about Imke de Pater (U. California, Berkeley), outer planets; Lindy Elkins- your astronomy course. We invite readers to write to us, respec- Tanton (Arizona State U.), lunar minerals and water; Beatriz tively, at Williams College, Hopkins Observatory, 33 Lab Campus Garcia (Pierre Auger Observatory, Argentina), cosmic rays; David Drive, Williamstown, MA 01267–2565, [email protected], and Ehrenreich (U. Geneva), exoplanets; Bruce Elmegreen (IBM) and Department of Astronomy, University of California, Berkeley, CA Clare Dobbs (U. Exeter), M51 modeling; Mansi Kasliwal (Caltech), 94720–3411, [email protected], or through the book’s web- Palomar Transient Factory and Zwicky Telescope Facility; Doug Gies sites. We promise a personal response to each writer.

Jay Pasachoff Alex Filippenko

A close-up view of the surface of dwarf planet Pluto, taken as NASA’s New Horizons spacecraft lew by on July 14, 2015, along with a full-disk view taken as the spacecraft approached. The heart-shaped region is Sputnik Planitia. At bottom right, in enhanced color, we see features that rise 1.5 miles high, scarred by clusters of pits 5–8 miles across and up to 1.5 miles deep, deeper than our Earth’s Grand Canyon. NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute