Brief Contents

Part One   Discovering the Science of Astronomy

Chapter 1 Beyond the Blue Horizon: A Grand Tour of the Universe 1-1
Chapter 2 Science and Pseudoscience 2-1
Chapter 3 Astronomical Observations: Angles and Uncertainties 3-1
Chapter 4 Basic Observations and Interpretations of the Sky 4-1
Chapter 5 The Historical Quest to Model the Solar System 5-1
Part Two   Discovering the Nature and Evolution of Planetary Systems
Chapter 6 The Structure and Formation of Planetary Systems 6-1
Chapter 7 The Smallest Objects of the Solar System 7-1
Chapter 8 The Earth and Moon: Processes and Facts 8-1
Chapter 9 The Earth-Like Planets 9-1
Chapter 10 The Jovian Planets 10-1
Part Three   Discovering the Techniques of Astronomy
Chapter 11 The Nature of Light 11-1
Chapter 12 Telescopes: Our Eyes of Discovery 12-1
Chapter 13 Spectra: The Key to Understanding the Universe 13-1
Part Four   Discovering the Nature and Evolution of Stars
Chapter 14 Understanding Stellar Spectra 14-1
Chapter 15 The Observed Properties of Normal Stars 15-1
Chapter 16 Energy Source and Structure of the Sun and Stars 16-1
Chapter 17 Star Formation and Evolution to the Main Sequence 17-1
Chapter 18 Stellar Evolution After the Main Sequence 18-1
Chapter 19 Stellar Death and Catastrophes 19-1
Part Five   Discovering the Nature and Evolution of Galaxies and the Universe
Chapter 20 The Milky Way: Our Galaxy 20-1
Chapter 21 Galaxies 21-1
Chapter 22 Active Galaxies and Quasars 22-1
Chapter 23 The Origin and Evolution of the Universe 23-1
Part Six   Discovering If There Is Life Elsewhere in the Universe
Chapter 24 The Search for Extraterrestrial Life 24-1

vi Contents
 Contents

Part One   Discovering the Science of Astronomy

Chapter 1 Chapter 2
Beyond the Blue Horizon: A Science and Pseudoscience
Grand Tour of the Universe 2.1 An Expedition to Earth  2-2
1.1 What Is Astronomy?  1-2 2.2 Astronomy as an Observational
1.2 Our View of the Cosmos  1-2 Science 2-4
Distances and Sizes  1-3 The Process of Doing
Astronomy 2-5
Time 1-5
The Astronomer’s Challenge  2-8
1.3 The Solar System  1-6 The Astronomical Time
The Star of the Solar System  1-6 Machine 2-9
The Earth-like Planets  1-7 2.3 Science as a Process  2-9
The Giant Planets  1-8 The Explosion of Knowledge
The Outer Reaches of the Solar in the Twentieth Century  2-9
System 1-10 From Idea to Textbook — How
Planets around Other Stars  1-10 Science Proceeds  2-11
Two Examples of Science as a
1.4 Stars, Galaxies, and Process 2-12
Beyond 1-10 The “Face” on Mars  2-12
The Martian Meteorite and Life  2-12
Interstellar Material and Star
Formation 1-11 2.4 Is It Science
Stellar Evolution  1-11 or Pseudoscience?  2-13
Clusters of Stars  1-12 The “Game” of Science  2-13
Galaxies 1-13 Is the Hypothesis at Risk?  2-15
Clusters of Galaxies  1-14 Ignoring accepted Facts  2-15
The Universe as a Whole  1-15 Simple Answers to Complex
Problems 2-15
1.5 Where Does Astronomy Go Playing the Underdog  2-16
from Here?  1-15 Conspiracy Theories  2-16

Contents vii
 Playing on Fear and Emotion  2-16 Ancient Observatories and
Observations
Do They Do Research?  2-17
Calendars 4-5
For Whom Do They Write?  2-17
2.5 Do New Ideas Displace 4.2 Early Greek Observations: The
Round Earth  4-5
the Old Ones?  2-18
Concluding Thoughts  2-18 4.3 The Observed Motions of the
Sky 4-7
The Celestial Sphere: A Model of
Chapter 3 the Sky  4-7
Astronomical Observations: 4.4 The Motion of the Sun  4-10
Angles and Uncertainties The Daily Motion  4-10
3.1 Angles and Angular The Motion of the Sun in Relation
Measurement 3-2 to the Stars  4-10
Solar and Sidereal Days  4-11
3.2 Angles on the Celestial
Sphere 3-3 4.5 The Reasons for the
Seasons 4-12
3.3 The Relationship between
Physical and Angular Size  3-4 4.6 The Location of Stars on the
Angular Size and Solar Celestial Sphere  4-13
Eclipses 3-6 Precession 4-14
3.4 Measurement Uncertainty  3-6 4.7 The Motion and Phases of the
Precision and Accuracy  3-6 Moon 4-15
Random Uncertainties  3-7 The Motion of the Moon  4-15
Systematic Uncertainty  3-8 The Phases of the Moon  4-15
3.5 Systematic Uncertainties Eclipses 4-17
in Astronomy: The Kapteyn Solar Eclipses  4-17
Lunar Eclipses  4-18
Universe as an Example  3-10
4.8 The Motions of the
Discovery 3-1: Measuring Your Planets 4-19
Room 3-12
4.9 How Stars Get Their
Names 4-21
Chapter 4 4.10 Measuring Star
Basic Observations and Brightness 4-22
Interpretations of the Sky
4.1 Early Observations of the
Sky 4-2
viii Contents
Appendix: Observing Hints Ptolemy 5-7
and the Use of Star Models: Revisited  5-7
Charts 4-22 5.2 Astronomy
Brightness of Stars  4-22 during the Middle Ages  5-7
Observing Stars in the Northern
Part of the Sky  4-23 5.3 The Heliocentric
The Northern Sky in September  4-23 Hypothesis 5-8
The Northern Sky at Other Times of the Nicolaus Copernicus  5-8
Year  4-23
Observing the Rest of the Sky: Using Tycho Brahe  5-10
the Star Maps  4-24 Johannes Kepler  5-11
Observing Tips  4-25
5.4 Kepler’s Laws of Planetary
Chapter 5 Motion 5-12
The Historical Quest to Model 5.5 The Search for
the Solar System Underlying Laws  5-15
5.1 Greek Astronomy  5-2 Galileo Galilei  5-15
What the Greeks Inherited  5-2 Isaac Newton  5-16
Aristotle 5-2 Newton’s Law of Gravity  5-18
Aristarchus of Samos  5-3 Weight 5-20
Eratosthenes 5-4 Momentum 5-20
Hipparchus 5-5 Newton’s Generalization
Other Deductions of the Greek of Orbital Motion  5-20
Astronomers: The Distances of the Newton’s Form of Kepler’s Third
Planets 5-5 Law 5-22
The Apparent Motions of the Successes of Newton’s Laws  5-22
Planets in Relation to the
Stars 5-5
5.6 Evidence in Favor
The Geocentric Model of the Solar
System 5-5 of the Heliocentric
The Hypothesis of Circular Hypothesis 5-23
Motion 5-6
5.7 Observational Evidence
of the Earth’s Rotation  5-25
Foucault Pendulum  5-25
Coriolis Effects  5-26
Precession 5-27

Contents ix
Discovery 5-1: Weightlessness  5-28
Part Two  Discovering the Nature and Evolution of
the Planetary Systems
Chapter 6 6.6 Other Planetary Systems  6-17
The Structure and Formation Methods of Search and
of Planetary Systems Discovery 6-18
6.1 An Overview of the Solar Properties of Extrasolar Planets
and their Stars  6-20
System 6-2
DISCOVERY 6-1: A Scale Model of
6.2 Observations: Orbital the Solar System  6-21
Patterns 6-5
6.3 The Distribution of Angular Chapter 7
Momentum 6-6
The Smallest Objects of the
6.4 Hypotheses of the Origin of the Solar System
Solar System  6-7 7.1 Pluto and the Trans-Neptunian
A Simple Hypothesis That Does Not
Work 6-7 Objects 7-2
Evolutionary Hypotheses  6-7 Future Spacecraft Study of
Pluto 7-6
Catastrophic Hypotheses  6-8
Additional Hypotheses  6-9
7.2 Comets  7-6
The Structure of Comets  7-7
6.5 Modern Ideas  6-9 The Dirty Snowball Model  7-8
Energy and Solar System
Formation 6-9 Orbits of Comets  7-9
The Role of Dust Grains in Planet The Oort Comet Cloud  7-10
Formation 6-10 Spacecraft Studies of Comets  7-11
Chemical Composition  6-10 Future Spacecraft Studies of
Bringing It All Together  6-12 Comets 7-13
Refinements of the Theory  6-14 7.3 Asteroids  7-13
Leftover Odds and Ends  6-14 Characteristics of Asteroids  7-13
The Angular Momentum Orbits of Asteroids  7-14
Problem 6-16
The Trojans and the Kirkwood
Which Hypothesis of Solar System Gaps 7-15
Formation Is Preferred?  6-16
Why Are Asteroids So Small?  7-16
Model Solar Systems  6-17
Chemical Composition  7-16

x Contents
 Other Spacecraft Studies of 8.3 Earth’s Surface  8-8
Asteroids 7-17
Rock Types, Processes, and Ages  8-8
7.4 Meteors, Meteor Showers, and Chemical Composition  8-9
Meteorites 7-18 Volcanism 8-9
Meteorite Craters  7-19
Mountains 8-10
Did an Asteroid or Comet
Impact Send the Dinosaurs into Impact Craters  8-10
Extinction? 7-19 Ocean Tides  8-10
Meteor Showers  7-21 Water 8-11
7.5 Interplanetary Dust  7-22 8.4 Earth’s Atmosphere  8-11
7.6 Meteorites and the Early Solar The Greenhouse Effect  8-12
System 7-23 Atmospheric Circulation  8-12
Chemical Composition  7-23 Origin and Maintenance of the
Atmosphere 8-13
Internal Structure  7-24
The Origin of Meteorites  7-25 8.5 Earth’s Magnetism  8-14
Meteorite Dating  7-26 8.6 The Moon: Large-Scale
Did a Supernova Explosion Trigger Characteristics   8-15
the Formation of Our Solar
System? 7-27 8.7 The Moon’s Atmosphere  8-16
Discovery 7-1: Asteroid Brightness 8.8 The Lunar Surface  8-16
Variations 7-29 General Surface
Characteristics 8-17
Craters 8-19
Chapter 8 Maria and Highlands  8-20
The Earth and Moon: Processes Surface Movement  8-23
and Facts Lava Channels and Tubes  8-23
8.1 Earth as an Astronomical The Composition and Structure
Body 8-2 of the Lunar Surface
Material 8-24
Determination of Basic
Properties 8-2 The Age of the Lunar Surface  8-26

8.2 Earth’s Interior  8-3 8.9 The Moon’s Interior  8-27

Seismic Studies  8-4 8.10 The Origin of the Moon  8-29
Plate Tectonics  8-6
8.11 Tides and the Future of the
The Source of Heat in the Earth-Moon System  8-32
Interior 8-7
8.12 Understanding the Universe
using the Moon   8-32
Contents xi
Discovery 8-1: Lunar Surface Continents, Mountains, and
Volcanoes 9-23
Features, As Seen from
Faults, Tectonics, Cliffs, and
Earth 8-34 Valleys 9-25
Wind Erosion  9-27
Chapter 9 Polar Regions  9-28
The Earth-Like Planets 9.5 Interiors  9-29
9.1 Introduction to the Terrestrial Magnetic Fields  9-29
Planets 9-2 Interior Structures  9-30
Early Ground-based Studies  9-2 9.6 Moons  9-30
Planetary Space Exploration  9-4
9.7 Evolutionary Comparison  9-31
9.2 Large-Scale Characteristics  9-5
Orbits 9-5
Chapter 10
Rotation 9-6
Basic Properties: Size, Mass,
The Jovian Planets
Density 9-8 10.1 Introduction  10-2
Seasons 9-8 An Overview of Ground-Based
Studies 10-2
9.3 Atmospheres  9-10 Space Exploration of Jovian
Atmospheric Chemical Planets 10-4
Composition 9-10
Atmospheric Temperature  9-11
10.2 Large-Scale
Atmospheric Pressure  9-12
Characteristics 10-4
Orbits and Rotation  10-4
Lightning 9-12
Size, Mass, Density  10-5
Clouds 9-12
Seasons 10-6
Atmospheric Circulation  9-13
Excess Energy  10-5
Why Do the Atmospheric
Compositions Differ So Much?  9-13 10.3 Atmospheres  10-6
9.4 Surfaces  9-14 Appearance and Circulation  10-7
The View from Orbit  9-14 Chemical Composition  10-9
The View from the Surface  9-15 10.4 Planetary Interiors  10-9
Surface Temperatures  9-16 Magnetic Fields  10-10
Surface Compositions  9-16 Interior Structure  10-11
Water 9-17
10.5 Moons  10-13
Craters 9-21
The Moons of Jupiter  10-13
Impact Basins  9-22
The Moons of Saturn  10-18
xii Contents
 The Moons of Uranus  10-22 10.7 Future Studies of the Jovian
The Moons of Neptune  10-24 Planets and Moons  10-30
10.6 Planetary Rings  10-25

Part Three  Discovering the Techniques of

Astronomy
Chapter 11 Chapter 12
The Nature of Light Telescopes: Our Eyes of
11.1 Light as a Ray  11-2 Discovery
Reflection 11-2
12.1 The Formation of
Refraction 11-2 Images 12-2
11.2 Light as a Wave  11-2 12.2 Telescopes 12-4
Diffraction 11-2 The Light-Gathering Power of a
Interference 11-3 Telescope 12-4
Electromagnetic Radiation  11-5 Resolving Power  12-6
The Speed of Light  11-6 Magnification 12-7
Speed, Frequency, and The Mounting of a Telescope  12-8
Wavelength 11-8
12.3 Comparing Reflecting
Polarization 11-9
and Refracting
11.3 Light as a Stream Telescopes 12-8
of Particles  11-10
12.4 Reflecting Telescopes
The Photoelectric Effect  11-11
of Various Types  12-9
The Compton Effect  11-12
So, What is Light?  11-12 12.5 The Telescopes
of the Future  12-11
Discovery 11-1: Images in a Efforts to Overcome the Unsteady
Mirror 11-14 Atmosphere 12-12
Discovery 11-2: Refraction of 12.6 Detectors and
Light 11-16 Instruments 12-12
Cameras and Film  12-13
Photoelectric Photometers  12-13
Modern Electronic Detectors  12-
13
Contents xiii
12.7 Radio Astronomy  12-14 The Laws of Blackbody
Radiation 13-5
Interferometers 12-16
Objects Can Be Seen by Their
12.8 Optical and Radio Observatory Emitted Light or Their Reflected
Light 13-7
Sites 12-18 Emission Spectra: Kirchhoff’s
12.9 Beyond Optical Second Law  13-7
and Radio Astronomy  12-19 The Spectral Fingerprints of the
Chemical Elements  13-8
12.10 NASA’s Great The Sun’s Absorption Spectrum:
Observatories 12-20 Kirchhoff’s Third Law  13-8
The Hubble Space Telescope  12-21 13.2  Understanding Spectra  13-9
The Compton Gamma-Ray Energy-Level Diagram of the
Observatory 12-22 Hydrogen Atom  13-12
The Chandra X-Ray Why Different Elements Have
Observatory 12-22 Different Spectra  13-15
The Spitzer Space Telescope  12-23 Atomic Explanation of Kirchhoff’s
Laws 13-15
The Future  12-23
13.3  Applications of
Spectroscopy 13-17
Chapter 13 A Model of the Sun Based
Spectra: The Key to on Its Spectrum  13-17
Understanding the Universe The Sun’s Flash Spectrum  13-17
13.1  Observations of Spectra  13-2 Ionized Gas between the Stars  13-
18
The Principle of the Why Nebulae Shine  13-18
Spectrometer 13-2
Forbidden-Line Emission  13-19
The Continuous Spectrum: Neutral Gas between the Stars:
Kirchhoff’s First Law  13-3 Interstellar Absorption Lines  13-
The Dependence of the Continuous 20
Spectrum on Temperature  13-4

Part Four  Discovering the Nature and Evolution of

Stars
Modern Classification  14-2
Chapter 14 Why are stellar Spectra
diverse? 14-5
Understanding Stellar Spectra Low-Temperature Stars  14-7
Medium-Temperature Stars  14-7
14.1 Classification of Stellar High-Temperature Stars  14-7
Spectra 14-2 Molecules in Cool Stars  14-8

xiv Contents
 Observations of Stellar 15.4 The Hertzsprung-Russell
Spectra 14-9
Diagram 15-11
14.2 The Cosmic Abundance of the A Graphing Experiment  15-11
Chemical Elements  14-10 Introduction to the Hertzsprung-
Russell Diagram  15-12
14.3 The Doppler Effect  14-12
The Nearest Stars  15-13
14.4 What We Can Learn from The Brightest Stars  15-13
Spectral Lines  14-15
Interpreting the Hertzsprung-
Thermal Broadening  14-15 Russell Diagram  15-14
Rotation of Stars  14-15
15.5 Main-Sequence,
Density in a Stellar
Atmosphere 14-16 Giant, Supergiant, and White
Atmospheric Turbulence  14-17 Dwarf Stars  15-15
Magnetic Fields in Stars  14-17 15.6 Explanation of the Main
Binary Stars  14-18 Sequence 15-17
A Final Example of Stellar The Mass–Luminosity Relation  15-
Spectra 14-18 17
Discovery 14-1: Classification of Densities of Stars: A Reprise  15-19
Stellar Spectra  14-19 15.7 Stellar Distances
and the H-R Diagram  15-20
Chapter 15 Discovery 15-1: Visual Binary
The Observed Properties of Stars 15-22
Normal Stars Discovery 15-2: Spectroscopic
15.1 Distance Measurements  15-2 Binary Stars  15-24
Variation of Stellar Brightness
with Distance  15-4
15.2 Binary Stars and Stellar Chapter 16
Masses 15-5 Energy Source and Structure of
Visual Binaries   15-5 the Sun and Stars
Spectroscopic Binaries  15-7 16.1  The Power Produced by the
Eclipsing Binaries  15-8 Sun 16-2
15.3 Binary Stars and Other Stellar 16.2  Energy Sources  16-3
Properties 15-9 Chemical Reactions  16-3
Lunar Occultations  15-9 Gravitational Collapse  16-3
Optical Interferometry  15-10 Nuclear Reactions: Fission versus
Fusion 16-4
Densities of Stars  15-11
Contents xv
 The Proton-Proton Chain  16-5 17.1 Matter for Star
The Carbon–Nitrogen–Oxygen Formation 17-2
Cycle 16-7
Dust and Molecules  17-2
16.3  The Conditions Required for Molecules in the Interstellar
Fusion 16-7 Medium 17-3
Temperatures and Densities  16-7 Dust in the Interstellar
Medium 17-4
16.4  Proof of Fusion in Stars  16-8 The Formation of Molecules in Dust
Clouds 17-5
16.5  Stellar Structure  16-11
The Hydrogen Molecule  17-6
Pressure and Energy
Equilibrium 16-11 Clouds and Cloud Complexes  17-6
Energy Transport  16-13 17.2 Star-Formation: Theory  17-7
Stellar Models  16-13 Initiation of Star Formation  17-7
16.6  The Lifetimes of Stars  16-15 Disk Formation and Accretion  17-8
16.7  The Sun—A Typical Star  16- Theoretical Models of Early
Stellar Evolution  17-9
17 The Approach to the Main
The Photosphere  16-17 Sequence 17-10
The Convective Zone  16-18 17.3 Star-Formation:
Sunspots 16-19 Observations 17-12
The Sun’s Magnetic Field  16-20 Bipolar Nebulae and Accretion
The Chromosphere  16-21 Disks 17-12
The Corona  16-22 Bok Globules  17-12
The Solar Wind  16-23 Infrared Sources  17-13
Flares and Other Surface Activity T Tauri and FU Orionis Stars  17-14
on the Sun  16-24 Herbig-Haro Objects  17-15
Solar-Terrestrial Connections  16- OB Associations  17-16
25
Brown Dwarfs  17-18
Solar Oscillations  16-25
Star Clusters  17-19
Discovery 16-1: Solar
Granulation 16-27 17.4 A Prominent Region of
Star Formation: The Orion
Molecular Cloud Complex and
Chapter 17 Nebula 17-21
Star Formation and Evolution
to the Main Sequence

xvi Contents
Chapter 18 Chapter 19
Stellar Evolution After the Stellar Death and Catastrophes
Main Sequence 19.1 Novae 19-2
18.1 The Mid-Life Evolution of Sun- Observations 19-2
like Stars  18-2 The Place of Novae in Stellar
Evolution 19-3
Why Stars Leave the Main
Sequence 18-2 Do Novae Involve Large or Small
Stars? 19-4
Becoming a Red Giant  18-4
How a Nova Explodes  19-4
Evolution during the Red Giant
Phase 18-4
19.2 Supernovae 19-5
18.2 The Mid-Life Evolution of Observations 19-6
Stars Less Massive Than the Thermonuclear Supernovae: Type
Sun 18-6 Ia   19-7
Core Collapse Supernovae: Type
18.3 The Mid-Life Evolution of Stars II   19-8
More Massive Than Eight Solar Type II Supernovae  19-9
Masses 18-7 Synthesis of Heavy Elements in
Massive Stars  19-12
18.4 Pulsating Stars  18-9
Confirmation of the Type II Model:
18.5 Mass Loss, Binary Stars, and Supernova 1987A  19-13
Stellar Evolution  18-10 19.3 Neutron Stars and
18.6 The Death of Stars Less Massive Pulsars 19-14
Than Eight Solar Masses  18- Pulsars 19-16
12 Why Pulsars “Pulse”  19-18
Planetary Nebulae  18-12 A Model of a Neutron Star  19-20
Observational Properties of White Binary and Millisecond
Dwarfs 18-16 Pulsars 19-20
The Structure of White Dwarfs  18- Magnetars 19-20
18 Planets around Pulsars  19-21
18.7 The Observational Evidence for 19.4 Black Holes  19-21
Stellar Evolution  18-19 The Theoretical Prediction of
Black Holes  19-21
The Hertzsprung-Russell Diagrams
of Star Clusters  18-19 How to Find and Recognize a Black
Hole 19-22
Evidence from Spectra Pertaining
to Stellar Evolution  18-21 Observations of Stellar Black
Holes 19-24
A Direct Detection of Stellar
Evolution 18-22

Contents xvii
19.5 Compact Objects in Binary Gamma-Ray Bursters  19-26
Systems 19-25 A General Model  19-27
Microquasars 19-25

Part Five  Discovering the Nature and Evolution of

Galaxies and the Universe
Chapter 20 Interstellar Gas  20-13
The Milky Way: Our Galaxy 21-cm Hydrogen Emission  20-14
The Structure of the Interstellar
Medium 20-15
20.1 Our Place in the Milky 20.4 The Structure of the Milky Way
Way 20-2 System 20-17
A Historical Overview  20-2 Optical Evidence for the Spiral
The Distribution of Globular Structure of the Galaxy  20-17
Clusters 20-3 Radio Evidence for the Spiral
Structure of the Galaxy  20-18
20.2 Characteristics of the Milky
The Cause of Spiral Structure  20-
Way 20-3 20
Rotation of Our Galaxy  20-5 The Density Wave Theory  20-21
The Mass of the Galaxy  20-7 The Galactic Halo and the Nuclear
Dark Matter  20-8 Bulge 20-22
High Velocity Stars in the The Center of the Galaxy  20-22
halo 20-9 Stellar Populations  20-24
20.3 Interstellar Gas and Dust  20-9 20.5 The Formation and Evolution
Interstellar Dust: Extinction of of the Galaxy  20-25
Starlight 20-9
The Chemical Evolution of the
Interstellar Dust: Reddening  20- Galaxy 20-26
10
The Formation of the Milky
Interstellar Dust: Reflection Way 20-26
Nebulae 20-11
Interstellar Dust: Polarization of 20.6 The Galactic Magnetic
Starlight 20-11 Field 20-27
Interstellar Dust: Thermal
Radiation 20-12 20.7 Cosmic Rays  20-28
Interstellar Dust: Chemical Observations of Cosmic Rays  20-28
Composition and Formation  20-12 Origin of Cosmic Rays  20-28

xviii Contents
Discovery 20-1: Galactic 21.5 The Star and Gas Content of
Rotation 20-29 Galaxies 21-15
Discovery 20-2: The Distributions Spiral Galaxies  21-15
of Different Objects around the Elliptical Galaxies  21-15
Galaxy 20-31 Irregular Galaxies  21-16
Discovery 20-3: The Scale of the Sizes, Separations and the Most
Common Galaxies  21-16
Milky Way  20-33
21.6 The Formation and Evolution
of Galaxies  21-17
Chapter 21 Differences between Spirals  21-18
Galaxies Elliptical Galaxies From
Spirals? 21-19
21.1 The Historical Problem of the
Violent Galaxy Interactions and
Nebulae 21-2 Mergers 21-20
21.2 The Morphology of 21.7 Clusters of Galaxies  21-22
Galaxies 21-3 Masses of Galaxy Clusters  21-22
Spiral Galaxies  21-4 The Cluster Environment and
Elliptical Galaxies  21-4 Galaxy Evolution  21-24
S0 Galaxies  21-4 Intergalactic Matter  21-24
Irregular Galaxies  21-5 21.8 Clusters of Clusters:
Dwarf Galaxies  21-6 Superclusters 21-25
Hubble’s Tuning Fork Diagram  21-6 21.9 Cluster and Supercluster
21.3 Distances of the Formation 21-27
Galaxies 21-7 Discovery 21-1: Distances
Cepheid Variables  21-7 Throughout the Universe  21-
Other Distance Indicators for 28
Galaxies 21-8
The Velocity–Distance
Relationship 21-9 Chapter 22
21.4 General Galaxy Active Galaxies and Quasars
Attributes 21-12 22.1 Seeing Galaxies in a New
Luminosity 21-12 Light 22-2
Dimensions 21-12 A Distant Powerful Radio Source:
Mass 21-13 Cygnus A  22-3
Centaurus A: Transporting Radio
Energy 22-4

Contents xix
 M87: the Active Galaxy Nucleus
Power Revealed  22-6
Chapter 23
The Origin and Evolution of
22.2 Other Active Galaxies: Seyfert the Universe
Galaxies, BL Lac Objects, and
Quasars   22-7 23.1 The Four Pillars of the Big
Seyfert Galaxies: Wild Spirals  22-7
Bang 23-2
The First Pillar: The Dark Night
BL Lac Objects: Looking Down the Sky 23-2
Monster’s Throat   22-8
The Second Pillar: Recession of The
Quasars: An Upsetting Puzzle  22-9 Galaxies 23-4
Quasar Spectra, Redshifts, The Third Pillar: The Cosmic
Distances, and Luminosities   22-9 Background 23-7
Quasar Variability  22-12 The Fourth Pillar: Light Element
Confirmation of Quasar Distances Abundances 23-11
and their Occurrence in
galaxies 22-12 23.2 Questions about the Big
Bang 23-12
22.4 The “Monster” Energy Source
Why is there any matter in the
for QSOs and AGNs   22-14 universe? 23-13
22.5 A Unified Model of AGN, BL Why is the universe the same in
opposite directions?   23-13
Lacs and Quasars  22-16
How was the Universe
Discovery 22-1: Measuring a Inflated?   23-14
Quasar’s Redshift  22-17 Does the Universe have an
Edge?   23-16
Discovery 22-2: A Scale Model of
Distances in the Universe  22-
23.3 Surprising Mysteries of the Big
Bang 23-18
18
A Surprising Result for the
Velocity-Distance Plot  23-18
Mysterious Origin of the
Acceleration 23-20
Convincing the dark
Energy Skeptics: WMAP 3K
Observations 23-22
23.4 Multiple Universes?  23-24
Discovery 23-1: The Expansion of
the Universe  23-26
Discovery 23-2: The Age of the
Universe 23-27

xx Contents
Chapter 24
Part Six  Discovering if There is Life Elsewhere in
The Search for the
Extraterrestrial
Universe Life
24.1 What is Life?  24-2 Modern Searches for
Life on Earth  24-2 Extraterrestrial Intelligence  24-
20
24.2 The Ingredients for Life  24-4 Should We Go There?  24-22
The Extreme Range of Life on What Do We Do When We Get
Earth 24-4 There?   24-22
A Source of Energy  24-6 Announcing Our Existence to the
Liquid Water  24-7 Universe   24-23
Carbon 24-8 Discovery 24-1: Exploring the
24.3 The Search for Extra- Conditions for Life  24-26
Terrestrial Life inside Our Solar
System 24-9
APPENDIX A  USEFUL MATHEMATICAL
The Moon and Mercury  24-10 INFORMATION A1
Venus 24-10
APPENDIX B Constellations A6
Mars 24-11
The Jovian Moons  24-13 APPENDIX C  Properties of Planets1 and
Moons A8
24.4 The Search for Life Outside Our
Solar System  24-15 APPENDIX D  The 40 Brightest
Stars A11
Stellar Habitable Zones  24-15
Galactic Habitable Zones  24-16 APPENDIX E  Stars Nearer than 4
Parsecs A12
The Search for Life on Worlds
Outside Our Solar System  24-16 APPENDIX F  Some Local Group
Galaxies A13
24.5 The Search for Extraterrestrial
Intelligence 24-17 APPENDIX G  Periodic Table of the
Elements A14
The Historical Search for
Extraterrestrial Intelligence  24-
18 APPENDIX H  Star Maps for the
Northern Hemisphere  A16
Is Anybody Out There?  24-19

Contents xxi