Astronomy: At Play in the Cosmos Read online

  ASTRON MY

  AT PL AY IN THE COSMOS

  ADAM FRANK

  u n i v e r s i t y o f r o c h e st e r

  w i t h co n t r i b u t i o n s by

  j e f f b a ry

  co lg at e u n i v e r s i t y

  c a r o l l at ta

  r o c h e s t e r ac a d e m y o f s c i e n c e

  nW. W. NORTON

  NEW YORK • LONDON

  W. W. Norton & Company has been independent since its founding in 1923, when William Warder Norton and Mary D. Herter Norton first published lectures delivered at the People’s Institute, the adult education division of New York City’s Cooper Union. The firm soon expanded its program beyond the Institute, publishing books by celebrated academics from America and abroad. By midcentury, the two major pillars of Norton’s publishing program—trade books and college texts—were firmly established.

  In the 1950s, the Norton family transferred control of the company to its employees, and today—with a staff of four hundred and a comparable number of trade, college, and professional titles published each year—W. W. Norton & Company stands as the largest and oldest publishing house owned wholly by its employees.

  Copyright © 2016 by W. W. Norton, Inc.

  All rights reserved

  Printed in Canada

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  ISBN 978-0-393-93522-6

  W. W. Norton & Company, Inc., 500 Fifth Avenue, New York, NY 10110-0017

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  1 2 3 4 5 6 7 8 9 0

  Adam Frank dedicates this book to Helene Detiler, Everett Boles, Keith Palen, Dutchie Armstrong, and “Miss T.”

  BRIEF C

  PART I  Bedrock

  1 Getting Started: Science, Astronomy, and Being Human 2

  2 A Universe Made, a Universe Discovered: The Night Sky and the Dawn of Astronomy 22

  3 A Universe of Universal Laws: From the Copernican Revolution to Newton’s Gravity 50

  4 A Universe of Universal Laws: How Light, Matter, and Heat Shape the Cosmos 76

  ONTENT

  PART II  Planets Near and Far

  5 The Architecture and Birth of Planetary Systems 104

  6 Home Base: Earth and the Moon 138

  7 Sibling Worlds: Mercury, Venus, and Mars 166

  8 Gas, Ice, and Stone: The Outer Planets 194

  9 Life and the Search for Habitable Worlds 224

  S

  PART III  A Galaxy of Stars

  10 The Sun as a Star 250

  11 Measuring the Stars: The Main Sequence and Its Meaning 274

  12 Nursery of the Stars: The Interstellar Medium and Star Formation 296

  13 To the Graveyard of Stars: The End Points of Stellar Evolution 324

  14 Down the Rabbit Hole: Relativity and Black Holes 350

  PART IV  A Universe of Galaxies

  15 Our City of Stars: The Milky Way 376

  16 A Universe of Galaxies 402

  17 The Cosmic Web: The Large-Scale Structure of the Universe 428

  18 Endings and Beginnings: Cosmology 454

  PART I

  Bedrock

  CONTENT

  2

  Preface xiii

  1GETTING STARTED

  A UNIVERSE MADE,

  Interactives xix

  Science, Astronomy,

  A UNIVERSE DISCOVERED

  About the Author xx

  and Being Human 2

  The Night Sky and the Dawn

  of Astronomy 22

  1.1 Miles Apart and Years

  Between 4

  2.1 An Old Obsession 24

  1.2 Very, Very Old and

  2.2 Dance of Night and Day:

  Really, Really Big 6

  Basic Motions of the Sky 24

  GOING FURTHER 1.1

  S

  GOING FURTHER 2.1

  Working with Scientific Notation 8

  The Small-Angle Formula 29

  1.3 Contents of the Cosmos 9

  2.3 Monthly Changes of the Moon 33

  1.4 Why Science? 12

  2.4 Celestial Wanderers:

  1.5 Science, Politics, and the Human

  The Motion of Planets 38

  Prospect on a Changing Planet 17

  2.5 Stone and Myth:

  chapter summary 19

  Astronomy before History 40

  questions and problems 20

  2.6 The Greek Invention

  of Science 43

  BIO:

  chapter summary 47

  Roald Hoffmann 15

  questions and problems 47

  BIO:

  Carol Latta 40

  BIO:

  Marcelo Gleiser 42

  vi

  PART II

  Planets Near

  and Far

  3

  4

  5

  A UNIVERSE OF

  A UNIVERSE OF

  THE ARCHITECTURE

  UNIVERSAL LAWS

  UNIVERSAL LAWS

  AND BIRTH OF

  From the Copernican Revolution

  How Light, Matter, and Heat

  PLANETARY SYSTEMS

  to Newton’s Gravity 50

  Shape the Cosmos 76

  104

  3.1 Getting Past Ptolemy:

  4.1 Light: The Cosmic Messenger 78

  5.1 The Rest of the Solar System 106

  The Copernican Revolution 52

  4.2 Astrophysical Spectra 81

  5.2 Just the Facts: A Solar

  3.2 Planets, Politics, and the

  System Census 107

  Observations of Tycho Brahe 55

  GOING FURTHER 4.1

  Wien’s Law 85

  5.3 Construction Debris: Asteroids,

  3.3 Kepler and the Laws

  Comets, and Meteoroids 111

  of Planetary Motion 56

  4.3 Spectra and the Strange

  World of the Atom 86

  5.4 Us versus Them: Our Solar

  GOING FURTHER 3.1

  System and Others 120

  Working with Kepler’s Third Law 60

  GOING FURTHER 4.2

  Brightness and Distance 93

  GOING FURTHER 5.1

  3.4 Galileo Invents New

  Orbit, Speed, and Velocity 127

  Sciences 60

  4.4 Telescopes 93

  5.5 Developing a Theory of

  3.5 Newto
n and the Universal

  4.5 Atmospheres and

  Planetary System Formation 129

  Laws of Motion 65

  Their Problems 95

  GOING FURTHER 5.2

  GOING FURTHER 3.2

  chapter summary 101

  Conservation of Angular

  Working with the Law of Gravity 68

  questions and problems 101

  Momentum 131

  GOING FURTHER 3.3

  chapter summary 135

  Acceleration Due to Gravity 69

  BIO:

  questions and problems 136

  Alyssa Goodman 86

  GOING FURTHER 3.4

  How to Weigh a Planet

  BIO:

  (Determine Its Mass) 70

  BIO:

  David Jewitt 120

  Pat Hartigan 90

  chapter summary 72

  questions and problems 73

  BIO:

  Heather Knutson 128

  BIO:

  Owen Gingerich 56

  BIO:

  Liliya Williams 67

  vii

  6

  7

  8

  HOME BASE

  SIBLING WORLDS

  GAS, ICE, AND STONE

  Earth and the Moon 138

  Mercury, Venus, and Mars 166

  The Outer Planets 194

  6.1 Discovering Change:

  7.1 Planet Stories 168

  8.1 Giant Planets on a Roll 196

  Crocodiles in the Arctic 140

  GOING FURTHER 7.1

  8.2 The Giant Planets:

  GOING FURTHER 6.1

  The Big Chill: The Rate of

  Structures and Processes 198

  Measuring Eternity:

  Planetary Cooling 169

  Radioactive Dating 141

  8.3 Jupiter: King of Planets 202

  7.2 Mercury: Swift, Small, and Hot 171

  6.2 Earth Inside and Out 142

  8.4 Saturn: Lord of the Rings 209

  7.3 Venus: Hothouse of the Planets 174

  6.3 Earth’s Near-Space

  GOING FURTHER 8.1

  Environment 148

  GOING FURTHER 7.2

  Rotation and Planetary Oblateness 211

  Planets without a Blanket: Temperature

  GOING FURTHER 6.2

  before Greenhouse Warming 179

  8.5 Uranus and Neptune:

  How to Keep an Atmosphere 150

  Ice Giants Discovered in Twilight 216

  7.4 Mars: The Red Planet

  6.4 The Closest Desolation:

  of Change 180

  chapter summary 221

  Earth’s Moon 155

  questions and problems 221

  chapter summary 191

  chapter summary 163

  questions and problems 191

  questions and problems 164

  BIO:

  Amanda Hendrix 202

  BIO:

  BIO:

  Jim Zimbelman 173

  John Tarduno 152

  BIO:

  Linda Spilker 216

  BIO:

  BIO:

  Jim Bell 182

  Jonathan Lunine 156

  viii

  PART III

  A Galaxy of Stars

  9

  10

  11

  LIFE AND THE SEARCH

  THE SUN AS A STAR

  MEASURING THE STARS

  FOR HABITABLE WORLDS

  250

  The Main Sequence

  224

  and Its Meaning 274

  10.1 Living with a Star 252

  9.1 The Origin of Life and the

  10.2

  11.1 The Life of the Stars 276

  The Sun’s Fusion Furnace 256

  Bottom of the World 226

  11.2 Measuring Stars 277

  9.2

  GOING FURTHER 10.1

  What Is Life, and Where

  Fusion, Matter, and E = mc 2 260

  Can It Exist? 226

  GOING FURTHER 11.1

  10.3

  Parallax 280

  Moving Energy 261

  GOING FURTHER 9.1

  11.3

  Calculating Habitable Zones 228

  10.4

  From Observations

  The Active Sun: Photosphere

  to Explanations 285

  9.3

  to Corona and Beyond 263

  The Origins of Life 232

  11.4 The March of Time: Stellar

  GOING FURTHER 10.2

  GOING FURTHER 9.2

  Evolutionary Tracks 289

  Sunspots and Temperature 264

  Time, Chance, and Life 234

  GOING FURTHER 11.2

  9.4

  chapter summary 271

  Searching for Other

  The Life Expectancy–Mass

  Life in the Universe 240

  questions and problems 272

  Relationship 290

  chapter summary 247

  chapter summary 293

  BIO:

  questions and problems 247

  questions and problems 294

  Lika Guhathakurta 254

  BIO:

  BIO:

  BIO:

  Chris McKay 233

  Jim Kaler 284

  Falk Herwig 262

  BIO:

  BIO:

  Woody Sullivan 244

  Harriet Dinerstein 291

  ix

  12

  13

  14

  NURSERY OF THE STARS

  TO THE GRAVEYARD

  DOWN THE RABBIT HOLE

  The Interstellar Medium and Star

  OF STARS

  Relativity and Black Holes 350

  Formation 296

  The End Points of

  Stellar Evolution 324

  14.1 The Black-Hole Shuffle 352

  12.1 Seeing in the Dark 298

  14.2 Special Theory of Relativity 353

  12.2

  13.1

  Anatomy of the ISM 299

  Fireworks, in a Galaxy

  Not So Very Far Away 326

  GOING FURTHER 14.1

  GOING FURTHER 12.1

  13.2

  The Simple Math of Time Dilation 358

  Pressure, Equilibrium, and the ISM 303

  From Giant to Dwarf: The Fate of

  Low- and Intermediate-Mass Stars 328

  14.3 General Theory of Relativity 360

  12.3 Molecular Clouds:

  14.4

  The Birthplace of Stars 306

  GOING FURTHER 13.1

  Anatomy of a Black Hole 364

  Why Red Giants Are Red and Giant 329

  12.4 From Cloud to Protostar 308

  GOING FURTHER 14.2

  13.3 The Evolution of a Massive Star 337

  Black-Hole Edges:

  GOING FURTHER 12.2

  The Event Horizon 367

  Star Formation and the

  chapter summary 347

  14.5

  Free-Fall Time 309

  questions and problems 348

  Real Black Holes in Astronomy 370

  12.5 From Protostars to Fusion

  chapter summary 373

  and Brown Dwarfs 315

  BIO:

  questions and problems 374

  Orsola De Marco 330

  12.6 Stellar Interaction 317

  BIO:

  chapter summary 321

  BIO:

  Sean Carroll 355

  questions and problems 321

  Stan Woosley 340

  BIO:

  BIO:

  Manuela Campanelli 366

  Judy Pipher 305

  BIO:

  Laura Arnold 311

  x

  PART IV

  A Universe of Galaxies

  15

  16

  17

  OUR CITY OF STARS

  A UNIVERSE

  THE COSMIC WEB
br />   The Milky Way 376

  OF GALAXIES

  The Large-Scale Structure

  402

  of the Universe 428

  15.1 A Hard Rain: Gaining a New

  Vision of Galactic Studies 378

  16.1 The Great Debate and the

  17.1 Bright Lights, Big Universe 430

  15.2 Anatomy of the Milky Way 381

  Scale of the Universe 404

  GOING FURTHER 17.1

  15.3

  16.2

  Hubble’s Constant and the

  Spiral Arms: Does the

  Galactic Zoology 405

  Age of the Universe 433

  Milky Way Have Them? 387

  16.3 The Cosmic Distance Ladder 412

  15.4

  17.2 Cosmic Neighborhoods: Galaxy

  The Galactic Center 390

  16.4 Monsters in the Deep:

  Groups and Galaxy Clusters 433

  GOING FURTHER 15.1

  Active Galactic Nuclei 417

  GOING FURTHER 17.2

  How to Bag a Black Hole

  GOING FURTHER 16.1

  Gravity and the Binding

  and Survive 393

  Hubble’s Law 418

  of Clusters 437

  15.5 Dark Matter and

  GOING FURTHER 16.2

  17.3 Superclusters and Large-

  the Milky Way 393

  AGN Variability 422

  Scale Structure 438

  GOING FURTHER 15.2

  16.5 Galaxies and Dark Matter 424

  17.4 Large-Scale Cosmic Structure

  Dark Matter and Galaxy Rotation 394

  and Cosmic History 444

  15.6

  chapter summary 425

  Constructing a Galaxy:

  17.5 Building Cosmic Structure 447

  Evolution of the Milky Way 397

  questions and problems 426

  chapter summary 451

  chapter summary 399

  BIO:

  questions and problems 451

  questions and problems 400

  David Law 414

  BIO:

  BIO:

  BIO:

  Eric Wilcots 435

  Bob Benjamin 385

  Paul Green 420

  BIO:

  BIO:

  Avi Loeb 444

  Debra Elmegreen 389

  xi

  18

  Appendices APP–1

  ENDINGS AND BEGINNINGS

  Selected Answers ANS–1

  Cosmology 454

  Glossary G–1

  18.1 How to Win a Nobel Prize 456

    Credits C–1

  18.2 Our Cosmology:

  The Big Bang 458

    Index I–1

  18.3 How Do We Know? The

  Three Observational Pillars

  of Big Bang Theory 465

  GOING FURTHER 18.1

  The CMB and the Expansion

  of the Universe 467

  18.4 Beyond the Classic

  Big Bang Model 467

  18.5 Questions about “Before”

  and “Everything” 473

  chapter summary 475

  questions and problems 475