Table of contents for Explorations : an introduction to astronomy.

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CONTENTS
PREFACE xix
PHOTO CREDITS FOR LOOKING UP FEATURES xxix
Preview
The Cosmic Landscape 1
P.1 The Earth, Our Home 2
P.2 The Moon 3
P.3 The Planets 4
P.4 The Sun 5
P.5 The Solar System 6
P.6 A Sense of Scale 6
P.7 The Astronomical Unit 7
P.8 The Milky Way Galaxy 7
P.9 The Light-Year 9
P.10 Galaxy Clusters and the Universe 10
P.11 Gravity 11
P.12 Atoms and Other Forces 11
P.13 The Still-Unknown Universe 12
P.14 The Scientific Method 12
I
The Night Sky 19
Chapter 1
History of Astronomy 19
1.1 Prehistoric Astronomy 20
The Celestial Sphere 21
Constellations 22
Motions of the Sun and Stars 23
Daily or Diurnal Motion 23
Annual Motion 24
The Ecliptic 25
Looking Up at Orion 26
The Seasons 28
The Ecliptic?s Tilt 29
Solstices and Equinoxes 30
The Planets and the Zodiac 32
The Moon 34
Extending Our Reach: Visibility of the Moon 36
Eclipses 38
1.2 Early Ideas of the Heavens: Classical Astronomy 40
The Shape of the Earth 40
The Size of the Earth 40
Distance and Size of the Sun and Moon 42
Extending Our Reach: Measuring the Diameter of Astronomical Objects 44
The Motion of the Planets 46
Ptolemy 47
Islamic Contributions 47
Asian Contributions 47
1.3 Astronomy in the Renaissance 48
Copernicus 48
Tycho and Kepler 49
Galileo 52
1.4 Isaac Newton and the Birth of Astrophysics 54
1.5 The Growth of Astrophysics 55
New Discoveries 55
New Technologies 55
The Nature of Matter and Heat 55
The Kelvin Temperature Scale 56
Projects 60
Essay 1
Backyard Astronomy 63
Learning the Constellations 63
Star Lore 64
Looking Up at the Summer Triangle 65
Amateur Astronomy 67
Small Telescopes 67
Star Charts 68
Celestial Coordinates 69
Planetary Configurations 70
Your Eyes at Night 72
PART II
Atoms, Forces, Light, and How We
Learn About the Universe 75
Chapter 2
Gravity and Motion 75
2.1 Solving the Problem of Astronomical Motion 76
2.2 Inertia 76
2.3 Orbital Motion and Gravity 78
2.4 Newton?s Second Law of Motion 79
Acceleration 79
Mass 80
2.5 The Law of Gravity 81
2.6 Newton?s Third Law of Motion 82
2.7 Measuring an Object?s Mass Using Orbital Motion 83
Extending Our Reach: Weighing the Sun 84
2.8 Surface Gravity 85
2.9 Escape Velocity 86
Chapter 3
Light and Atoms 91
3.1 Properties of Light 92
The Nature of Light?Waves or Particles? 92
Light and Color 94
Characterizing Electromagnetic Waves by Their Frequency 95
White Light 95
3.2 The Electromagnetic Spectrum: Beyond Visible Light 96
Infrared Radiation 96
Ultraviolet Light 97
Radio Waves 97
Other Wavelength Regions 98
Energy Carried by Electromagnetic Radiation 98
Radiation and Temperature 99
Extending Our Reach: Taking the Temperature of the Sun 100
Blackbodies and Wien?s Law 101
3.3 Atoms 101
Structure of Atoms 101
The Chemical Elements 103
3.4 The Origin of Light 104
3.5 Formation of a Spectrum 105
How a Spectrum Is Formed 105
Identifying Atoms by Their Light 107
Types of Spectra 109
Analyzing the Spectrum 111
Astronomical Spectra 111
3.6 The Doppler Shift: Detecting Motion 113
3.7 Absorption in the Atmosphere 114
Chapter 4
Telescopes 119
4.1 Telescopes 120
Light-Gathering Power 120
Focusing the Light 120
Extending Our Reach: Refraction 121
Resolving Power 127
4.2 Interferometers 129
4.3 Observatories 129
4.4 Detecting the Light 131
4.5 Observing at Nonvisible
Wavelengths 131
Extending Our Reach: Exploring New Wavelengths: Gamma Rays 134
Extending Our Reach: Observing the Crab Nebula at Many Wavelengths 134
4.6 Observatories in Space 135
Looking Up at Taurus 136
Atmospheric Blurring 138
Space Observatories versus Ground-Based Observatories 139
4.7 Going Observing 140
4.8 Computers 142
Projects 145
PART III
The Earth and Moon 147
Chapter 5
The Earth 147
5.1 The Earth as a Planet 148
Shape and Size of the Earth 148
Composition of the Earth 149
Density of the Earth 150
5.2 The Earth?s Interior 151
Probing the Interior with Earthquake Waves 151
Extending Our Reach: Measuring the Earth?s Mass 151
Heating of the Earth?s Core 154
5.3 The Age of the Earth 156
5.4 Motions in the Earth?s Interior 157
Convection in the Earth?s Interior 157
Plate Tectonics 158
5.5 The Earth?s Atmosphere 161
Composition of the Atmosphere 161
Origin of the Atmosphere 161
Extending Our Reach: Measuring the Motion of Plates Across Time 162
The Ozone Layer 165
The Greenhouse Effect 165
Structure of the Atmosphere 166
5.6 The Earth?s Magnetic Field 167
Origin of the Earth?s Magnetic Field 168
Magnetic Effects in the Upper Atmosphere 168
5.7 Motions of the Earth 170
Air and Ocean Circulation: The Coriolis Effect 170
Precession 172
Looking Up at the Northern Circumpolar Constellations 174
Project 177
Essay 2
Length of the Daylight Hours 179
The Day 179
Time Zones 182
Universal Time 182
Daylight Saving Time 182
The Month 183
The Calendar 184
Leap Year 184
Religious Calendars 184
Other Calendars 185
Names of the Months and Days 185
The Abbreviations A.M., P.M., B.C., and A.D. 185
Summary 186
Chapter 6
The Moon 189
6.1 Description of the Moon 190
General Features 190
Surface Features 190
Origin of Lunar Surface
Features 193
6.2 Structure of the Moon 195
Crust and Interior 195
The Absence of a Lunar Atmosphere 197
6.3 Orbit and Motions of the Moon 197
The Moon?s Rotation 198
Oddities of the Moon?s Orbit 198
6.4 Origin and History of the Moon 199
6.5 Eclipses 201
Rarity of Eclipses 202
Appearance of Eclipses 204
6.6 Tides 206
Cause of Tides 207
Solar Tides 209
Tidal Braking 210
6.7 Moon Lore 211
Project 214
PART IV
The Solar System 215
Chapter 7
Survey of the Solar System 215
7.1 Components of the Solar System 217
The Sun 217
The Planets 217
Two Types of Planets 220
Satellites 221
Asteroids and Comets 221
Composition Differences Between the Inner and Outer Planets 222
Density as a Measure of a Planet?s Composition 222
Extending Our Reach: Bode?s Law: The Search for Order 223
Age of the Solar System 224
7.2 Origin of the Solar System 225
Interstellar Clouds 225
Formation of the Solar Nebula 226
Condensation in the Solar Nebula 227
Accretion and Planetesimals 228
Formation of the Planets 228
Science at Work: Direct Formation of Giant Planets 229
Formation of Moons 230
Final Stages of Planet Formation 230
Formation of Atmospheres 232
Cleaning up the Solar System 232
7.3 Other Planetary Systems 232
Science at Work: Migrating Planets 234
Chapter 8
The Terrestrial Planets 239
8.1 Portraits of the Terrestrial Planets 240
8.2 Mercury 242
Mercury?s Temperature and Atmosphere 244
Mercury?s Interior 244
Mercury?s Rotation 245
8.3 Venus 246
The Venusian Atmosphere 247
The Greenhouse Effect 248
The Surface of Venus 248
The Interior of Venus 251
Rotation of Venus 252
8.4 Mars 252
The Martian Atmosphere 256
The Martian Interior 259
The Martian Moons 259
Life on Mars? 260
8.5 Why Are the Terrestrial Planets So Different? 261
Role of Mass and Radius 261
Role of Internal Activity 261
Role of Sunlight 261
Role of Water Content 262
Role of Biological Processes 262
8.6 Update: Exploring Mars 263
Chapter 9
The Outer Planets 271
9.1 Jupiter 272
Jupiter?s Appearance and Physical Properties 272
Jupiter?s Interior 273
Jupiter?s Atmosphere 274
Jupiter?s Ring 276
Jupiter?s Moons 277
9.2 Saturn 281
Saturn?s Appearance and Physical Properties 281
Saturn?s Rings 282
Origin of Planetary Rings 284
The Roche Limit 284
Saturn?s Moons 285
9.3 Uranus 285
Uranus?s Structure 287
Uranus?s Rings and Moons 288
Uranus?s Odd Tilt 288
9.4 Neptune 290
Neptune?s Structure 291
Neptune?s Atmosphere 291
Neptune?s Rings and Moons 292
9.5 Pluto 293
Chapter 10
Meteors, Asteroids, and Comets 299
10.1 Meteors,Meteoroids, and Meteorites 300
Heating of Meteoroids 300
Meteorites 301
11.3 Probing the Sun?s Core 332
Solar Neutrinos 333
Science at Work: Solving the Neutrino Puzzle 334
Solar Seismology 334
11.4 Solar Magnetic Activity 335
Sunspots 335
Solar Magnetic Fields 335
Prominences and Flares 336
Heating of the Chromosphere and Corona 338
Extending Our Reach: Detecting Magnetic Fields: The Zeeman Effect 339
The Solar Wind 340
11.5 The Solar Cycle 341
Cause of the Solar Cycle 342
Changes in the Solar Cycle 343
Links Between the Solar Cycle
and Terrestrial Climate 344
Projects 347
10.2 Asteroids 302
Size and Shape 302
Composition 304
Origin of Asteroids 305
Unusual Asteroids 305
10.3 Comets 307
Structure of Comets 307
Composition of Comets 309
Origin of Comets 309
Formation of the Comet?s Tail 310
Light from the Comet?s Tail 311
Short-Period Comets and the
Kuiper Belt 312
Science at Work: Kuiper Belt Objects and Beyond 313
Fate of Short-Period Comets 313
Meteor Showers 313
10.4 Giant Impacts 315
Giant Meteor Craters 316
Mass Extinction and Asteroid/Comet Impacts 317
Science at Work: Ghost Craters or No Tell-Tale Fragments 317
Science at Work: Meteorites Can Be Deadly 318
Projects 321
PART V
Stars 323
Chapter 11
The Sun, Our Star 323
11.1 Size and Structure 324
Measuring the Sun?s Properties 325
The Solar Interior 325
Energy Flow in the Sun 326
The Solar Atmosphere 327
11.2 How the Sun Works 328
Internal Balance (Hydrostatic Equilibrium) 329
Pressure in the Sun 329
Powering the Sun 330
Nuclear Fusion 331
The Structure of Hydrogen and Helium 331
The Proton?Proton Chain 331
Chapter 12
Measuring the Properties
of Stars 349
12.1 Measuring a Star?s Distance 350
Measuring Distance by Triangulation and Parallax 350
Extending Our Reach: Measuring the Distance to Sirius 353
Measuring Distance by the Standard-Candles Method 354
12.2 Measuring the Properties of Stars from Their Light 354
Temperature 354
Luminosity 355
The Inverse-Square Law and Measuring a Star?s Luminosity 356
Radius 357
The Stefan-Boltzmann Law 357
Extending Our Reach: Measuring the Radius of the Star Sirius 359
The Magnitude System 360
12.3 Spectra of Stars 361
Measuring a Star?s Composition 362
How Temperature Affects a Star?s Spectrum 362
Classification of Stellar Spectra 363
Science at Work: New Spectrum Classes 364
Definition of the Spectral Classes 364
Measuring a Star?s Motion 365
12.4 Binary Stars 368
Visual and Spectroscopic Binaries 368
Looking Up at Ursa Major 369
Measuring Stellar Masses with Binary Stars 370
Eclipsing Binary Stars 371
12.5 Summary of Stellar Properties 372
12.6 The H-R Diagram 373
Constructing the H-R Diagram 373
Analyzing the H-R Diagram 373
Giants and Dwarfs 374
The Mass?Luminosity Relation 375
Luminosity Classes 375
Summary of the H-R Diagram 376
12.7 Variable Stars 377
12.8 Finding a Star?s Distance by the Method of Standard Candles 379
Project 383
Chapter 13
Stellar Evolution 385
13.1 The Evolution of a Star 386
The Sun?s Life Story 387
The Life Story of a High-Mass Star 388
The Importance of Gravity 389
13.2 Star Formation 390
Interstellar Gas Clouds 390
Protostars 390
Bipolar Flows from Young Stars 392
Stellar Mass Limits 394
13.3 Main-Sequence Stars 394
Why a Star?s Mass Determines Its Core Temperature 395
Structure of High-Mass and Low-Mass Stars 395
Main-Sequence Lifetime of a Star 395
13.4 Giant Stars 396
Leaving the Main Sequence 396
Nuclear Fuels Heavier Than Hydrogen 397
Degeneracy in Low-Mass Stars 398
13.5 Yellow Giants and Pulsating Stars 398
Why Do Stars Pulsate? 399
The Period?Luminosity Law 400
13.6 Death of Stars Like the Sun 401
Ejection of a Low-Mass Star?s Outer Layers 401
Science at Work: Planetary Nebulas 401
Planetary Nebulas 402
13.7 Old Age of Massive Stars 404
Formation of Heavy Elements:Nucleosynthesis 404
Core Collapse of Massive Stars 405
Supernova Explosions 406
Supernova Remnants 406
13.8 History of Stellar Evolution Theories 409
13.9 Testing Stellar Evolution Theory 409
Extending Our Reach: Measuring the Age of a Star Cluster 410
Chapter 14
Stellar Remnants: White Dwarfs, Neutron Stars, and Black Holes 415
14.1 White Dwarfs 416
General Properties, Origin, and Fate 416
Structure of White Dwarfs 417
Degeneracy and the Chandrasekhar Limit 418
White Dwarfs in Binary Systems: Novas and Supernovas of Type I 419
14.2 Neutron Stars 421
General Properties and Origin 421
Pulsars and the Discovery of Neutron Stars 421
Emission from Neutron Stars 423
Structure of Neutron Stars 425
Neutron Stars in Binary Systems 425
X-Ray Binary Stars 425
14.3 Black Holes 426
The Formation and Observation of Black Holes 429
Gravitational Waves from Double Compact Stars 430
Hawking Radiation 431
The Milky Way and Other
Galaxies 435
Chapter 15
The Milky Way Galaxy 435
15.1 Discovering the Milky Way 435
Shape of the Milky Way 437
Size of the Milky Way 438
Looking Up at Sagittarius 440
15.2 Overview of the Milky Way 441
Structure and Contents 441
Mass of the Milky Way and the Number of Stars 442
Age of the Milky Way 443
15.3 Stars of the Milky Way 443
Stellar Censuses 443
Two Stellar Populations: Population I and Population II 444
Star Clusters 446
15.4 Gas and Dust in the Milky Way 448
Distribution and Composition of Interstellar Matter 448
Interstellar Dust: Dimming and Reddening 448
Interstellar Gas 451
Visible Emission from Interstellar Gas 451
RadioWaves fromCold Interstellar Gas 453
15.5 Motion of Stars and Gas in the Milky Way 453
Extending Our Reach: Mapping the Milky Way with Radio Waves 454
15.6 Measuring the Milky Way 457
Diameter of the Milky Way 457
Mass of the Milky Way 458
Extending Our Reach: Measuring the Mass of the Milky Way 458
Extending Our Reach: Measuring the Sun?s Speed Around the Milky Way 460
15.7 The Galactic Center 460
15.8 Formation of the Milky Way 462
Birth of Population I and II Stars 462
Building by Mergers 463
Population III 464
The Future of the Milky Way 465
Project 468
Chapter 16
Galaxies 469
16.1 Discovering Galaxies 470
Early Observations of Galaxies 470
Looking Up at M31 & Perseus 471
Types of Galaxies 473
Differences in the Stellar and Gas Content of Galaxies 476
The Cause of Galaxy Types 478
Galaxy Collisions and Mergers 479
16.2 Measuring the Properties of Galaxies 482
Galaxy Distances 482
The Redshift, and the Hubble Law 482
Extending Our Reach: Measuring theDistance of a Galaxy Using Cepheid Variables 483
Measuring the Diameter of a Galaxy 485
Extending Our Reach: Other Ways to Measure a Galaxy?s Distance 485
Measuring the Mass of a Galaxy 486
16.3 Dark Matter 486
16.4 Active Galaxies 488
Radio Galaxies 488
Seyfert Galaxies 489
Quasars 489
Cause of Activity in Galaxies 490
Extending Our Reach: Measuring the Diameter of Astronomical Objects by Using Their 
Light Variability 492
Science at Work: Explaining Jets 493
16.5 Quasars as Probes of Intergalactic Space 494
Gravitational Lenses 494
Extending Our Reach: Dark Matter and Gravitational Lenses 496
16.6 Galaxy Clusters 496
The Local Group 496
Rich and Poor Galaxy Clusters 497
Superclusters 499
Project 504
Chapter 17
Cosmology 505
17.1 Observations of the Universe 506
Distribution of Galaxies 506
Motion of Galaxies 507
Age of the Universe 508
Extending Our Reach: Estimating the Age of the Universe 509
The Cosmic Horizon 509
The Size of the Universe 510
Are We at the Center of the Universe? 510
Olbers? Paradox 511
The Cosmic Microwave Background 512
Composition of the Oldest Stars 514
Deductions from Basic Observations of the Universe 514
17.2 Evolution of the Universe: Expansion Forever or Recollapse? 515
The Density of the Universe 515
A Cosmological Repulsion? 516
Science at Work: The Universe?s Fate 518
17.3 The Shape of the Universe 518
17.4 The Origin of the Universe 520
Radiation,Matter, and Antimatter in the Early Universe 521
History of Matter and Radiation in the Early Universe 521
The Formation of Galaxies 523
17.5 The Inflationary Universe 524
The Flatness Problem 524
The Horizon Problem 525
Extending Our Imagination: Other Universes? 525
Essay 3
erse 529
Life on Earth 529
History of Life on Earth 529
Unity of Living Beings 530
Deductions from the Unity of Life and the Time Line 532
Origin of Life on Earth 532
Origin of Complex Organisms 533
Panspermia 533
Life Elsewhere in the Universe 533
Are We Alone? 534
Arguments for Many Worlds 534
Loners 535
Searching for Life Elsewhere 535
Radio Searches 535
The Gaia Hypothesis 536
The Anthropic Principle 537
Answers to ?Test Yourself? 539
Appendix 541
Powers-of-Ten Notation 541
Some Useful Formulas 541
Solving Distance,Velocity, Time (D, V, t ) Problems 542
Table 1 Physical and Astronomical Constants 542
Table 2 Conversion Between American and Metric Units 543
Table 3 Physical Properties of the Planets 543
Table 4 Orbital Properties of the Planets 543
Table 5 Satellites of the Solar System 544
Table 6 Meteor Showers 545
Table 7 The Constellations 546
Table 8 The Brightest Stars 548
Table 9 The Nearest Stars 549
Table 10 Properties of Main-Sequence Stars 550
Table 11 Periodic Table of Elements 551
Glossary 553
Index 567

Library of Congress Subject Headings for this publication:

Astronomy -- Textbooks.