On the Edge of the Cosmos, livre ebook

In a world where intergalactic wars are a common topic for movies, it is hard to imagine that the discovery of galaxies was made less than a century ago. In fact, it was one of the key astrophysical milestones of the first half of the 20th century, along with the revelation of the expansion of the Universe and the understanding of the source of the stars’ energy.

The second half of last century saw the unexpected discovery of fantastic objects and extreme events in the Universe including neutron stars, black holes, radio galaxies, quasars, exoplanets, or stellar explosions.Modern cosmology was simultaneously established with the Big Bang model, leading to an astonishingly precise determination of the parameters of the Universe.

The author here retraces the adventure of twentieth-century astronomy and describes how it has changed our vision of the cosmos. By assessing the major successes of this undertaking and highlighting the fundamental questions that still remain, he puts into perspective the recent progress at the dawn of the new millennium including the acceleration of the expansion of the Universe and dark energy, dark matter, exoplanets, black hole mergers and gravitational waves, to name only the most spectacular discoveries. This book thus offers, in a concise and accessible form, a synthesis of our current knowledge of astrophysics, including many beautiful images from leading observatories.

Contents

General Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII

Part I A Century of Revolution in Our Vision of the Universe . . . . . . . . . . 1

CHAPTER 1

General View of 20th Century Astronomy and Its Starting Point . . . . . . . . . 3

1.1 Astronomy, the Key to Our Vision of the World . . . . . . . . . . . . . . . . . 3

1.2 Benchmarks on 1900 Astronomy and Its Shortcomings . . . . . . . . . . . . 7

CHAPTER 2

Scientific and Technical Revolutions, Drivers of 20th Century Astronomy . . . 21

2.1 Physics Revolutions, Keys to Astrophysics . . . . . . . . . . . . . . . . . . . . . 21

2.2 Giant Telescopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.3 Overcoming the Disturbances of the Earth Atmosphere. . . . . . . . . . . . 24

2.4 Exploiting All Spectral Domains from Radio to X-ray and Gamma-ray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2.5 Visiting the Planets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2.6 No Pause in the Progress of Signal Detection and Exploitation . . . . . . 35

Part II Stars are Well Understood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

CHAPTER 3

How does a Star Work? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.1 Understanding the Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.2 Solving the Mystery of the Origin of the Energy of the Sun and the Stars . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 42

3.3 The Life of the Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.4 Our Atoms were Born in the Stars . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

3.5 Stars also Die . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

CHAPTER 4

Complexities of Star Birth and Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.1 General Star Formation Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.2 Young Infrared Stars: Born in Dusty Cocoons . . . . . . . . . . . . . . . . . . . 59

4.3 Gravitational Contraction, Accretion and Discs. . . . . . . . . . . . . . . . . . 59

4.4 Universality of Stellar Pairs – Complex Ending of Their Lives . . . . . . . 61

4.5 Brown Dwarfs, Billions of Aborted Stars . . . . . . . . . . . . . . . . . . . . . . . 63

4.6 Stars are Still at the Forefront of Current Astronomy . . . . . . . . . . . . . 65

4.7 Stars and Ecology of Planets and Galaxies . . . . . . . . . . . . . . . . . . . . . 68

Part III The New World of Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

CHAPTER 5

Discovery of Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

5.1 The Appreciation of the Nature of Galaxies Dates Back Only to the Beginning of the 20th Century . . . . . . . . . . . . . . . 73

5.2 First Steps in the World of Nearby Galaxies . . . . . . . . . . . . . . . . . . . . 77

5.3 Architecture and Stellar Content of Galaxies . . . . . . . . . . . . . . . . . . . . 81

CHAPTER 6

Our Galaxy and Its Interstellar Medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

6.1 Exploration of Our Galaxy, the Milky Way . . . . . . . . . . . . . . . . . . . . . 83

6.2 An Ordinary Galaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

6.3 Current Organization of Stars Resulting from the Milky Way History . 86

6.4 The Interstellar Gas, a Key Player in the Evolution of Galaxies . . . . . 86

6.5 Other Players in the Interstellar Medium . . . . . . . . . . . . . . . . . . . . . . 90

6.6 Exotic Components of the Milky Way . . . . . . . . . . . . . . . . . . . . . . . . . 94

CHAPTER 7

Hundreds of Billions of Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

7.1 Galaxies at All Stages of Their Life . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

7.2 The Turbulent Family Life of Galaxies . . . . . . . . . . . . . . . . . . . . . . . . 99

7.3 Understanding the Formation and Evolution of Galaxies . . . . . . . . . . . 106

Part IV Cosmology, the Science of the Universe as a Whole . . . . . . . . . . . . 109

CHAPTER 8

Birth of Cosmology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

8.1 The Universe of Galaxies is Expanding . . . . . . . . . . . . . . . . . . . . . . . . 111

8.2 The Saga of the Big Bang Confirmation . . . . . . . . . . . . . . . . . . . . . . . 114

8.3 The Very First Phase in the History of the Universe: Uncertain Physics . . . . . . . . . . . . . . . . . . . . . 116

8.4 AWell-Understood Second Phase: The Standard Big Bang Model . . . . 118

CHAPTER 9

Content of the Universe and Structure Formation . . . . . . . . . . . . . . . . . . . . . 123

9.1 Formation of Galaxies and Structures of the Present Universe . . . . . . . 123

9.2 Fundamental Parameters of the Universe are Better Known than Its Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

9.3 Age of the Universe and Variations of the Determinations of the Hubble Constant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

9.4 An Overall Density Very Close to the Critical Density . . . . . . . . . . . . 128

9.5 Need and Nature of Dark Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

9.6 A Last-Minute Surprise, the Re-Acceleration of the Expansion Involving an Unknown Source of Cosmic Energy . . . . . . . . . . . 131

9.7 Summarizing: An Unexpected Universe Model Validated in Multiple Ways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

Part V Singular Stars and Cataclysms in Extreme Physical Conditions . . . 135

CHAPTER 10

Explosions of Stars and Their Singular Residues . . . . . . . . . . . . . . . . . . . . . . 137

10.1 Extreme Physics of Supernova Implosion/Explosion . . . . . . . . . . . . . 137

10.2 Neutron Stars, Hyper-Dense Supernova Residues. . . . . . . . . . . . . . . . 145

10.3 Gamma-Ray Bursts, Even More Powerful Bursts . . . . . . . . . . . . . . . . 147

10.4 Cosmic Rays, Messenger Particles of the High Energy Universe . . . . . 149

CHAPTER 11

Black Holes and Their Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

11.1 Black Holes, General Relativity and the Cosmos . . . . . . . . . . . . . . . . 155

11.2 Stellar Black Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

11.3 GravitationalWaves, Propagation of Spacetime-Curvature Disturbances. . . 158

11.4 Quasars: New Stars a Thousand Times Brighter than Galaxies . . . . . 162

11.5 Manifestations of Super-Massive Black Holes and Their Interpretation . . . 164

11.6 Co-evolution of Galaxies and Their Black Hole . . . . . . . . . . . . . . . . . 170

11.7 The Super-Massive Black Hole of Our Galaxy and Others . . . . . . . . . 171

Part VI Planets, in the Solar System and Outside . . . . . . . . . . . . . . . . . . . 173

CHAPTER 12

Direct Exploration of the Planets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

12.1 Planets, Stars of Astronomy until the 19th Century . . . . . . . . . . . . . 175

12.2 Half a Century Without Revolution for Planetology . . . . . . . . . . . . . 178

12.3 Humans Went to the Moon! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

12.4 We Broadly Understand the Origin of the Moon and Its Importance for the Earth . . . . . . . . . . . . . . . . . . . . . . 181

12.5 Very Rich Close-up Photos of All the Bodies of the Solar System . . . 183

12.6 Summary of Planetary Expeditions . . . . . . . . . . . . . . . . . . . . . . . . . . 184

12.7 Searching for Life in the Solar System: Where and When? . . . . . . . . . 191

CHAPTER 13

Entering the Dream World of Exoplanets . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

13.1 Explosion of Discoveries of New Planets . . . . . . . . . . . . . . . . . . . . . . 197

13.2 The Majority of Stars have a Planetary System. . . . . . . . . . . . . . . . . 201

13.3 Surprising Variety of Exoplanets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

13.4 The Search for Earth-Like Planets. . . . . . . . . . . . . . . . . . . . . . . . . . . 204

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

CHAPTER 14

A New Cosmos in the 21st Century?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

14.1 A New Cosmos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

14.2 Auguries for 21st Century Astronomy? . . . . . . . . . . . . . . . . . . . . . . . 212

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

Acronyms and Space Missions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

The asterisks * indicate words or acronyms whose meaning is explained in the

“Glossary” or “Acronyms and space missions” sections at the end of the book.