"Presents the story of the black hole that has been suspected for over thirty years to exist there, but for which the evidence has dramatically firmed up in the last five years." - Martin Rees, Cambridge University.
Could Einstein have possibly anticipated directly testing the most captivating prediction of general relativity, that there exist isolated pockets of spacetime shielded completely from our own? Now, almost a century after that theory emerged, one of the world's leading astrophysicists presents a wealth of recent evidence that just such an entity, with a mass of about three million suns, is indeed lurking at the center of our galaxy, the Milky Way--in the form of a supermassive "black hole"! With this superbly illustrated, elegantly written, nontechnical account of the most enigmatic astronomical object yet observed, Fulvio Melia captures all the excitement of the growing realization that we are on the verge of actually seeing this exotic object within the next few years. Melia traces our intellectual pilgrimage to the "brooding behemoth" at the heart of the Milky Way. He describes the dizzying technological advances that have recently brought us to the point of seeing through all the cosmic dust to a dark spot in a clouded cluster of stars in the constellation Sagittarius.Carefully assembling the compelling circumstantial evidence for its black hole status, he shows that it is primed to reveal itself as a glorious panorama of activity within this decade--through revolutionary images of its "event horizon" against the bright backdrop of nearby, radiating gas. Uniquely, this book brings together a specific and fascinating astronomical subject--black holes--with a top researcher to provide both amateur and armchair astronomers, but also professional scientists seeking a concise overview of the topic, a real sense of the palpable thrill in the scientific community when an important discovery is imminent.
PREFACE vii 1. THE GALACTIC CENTER 1 1.1 The Hidden Realm 3 1.2 Removing the Dusty Veils 10 1.3 The Principal Constituents 18 1.4 Stars 37 2.2 The Motion of Stars and Gas 39 2.3 The Missing Mass 44 2.4 A 51 3.2 Development of a Gravity Theory 61 3.3 Everything Is Relative 69 3.4 The Principle of Equivalence 77 3.5 The Key Predictions of General Relativity 83 3.6 Black Holes and Their Event Horizons 94 4. A STAR IN SAGITTARIUS 105 4.1 Hawking Radiation 106 4.2 Energy Extraction according to Penrose 111 4.3 Cosmic Fireworks 114 4.4 Shape and Size of Sagittarius A* 117 4.5 The Glow of Matter Falling In 122 5. THE EVENT HORIZON 129 5.1 The Environment near the Precipice 131 5.2 How the Dark Shadow Forms 134 5.3 An Image of the Black Hole within This Decade 143 5.4 An X-Ray Image of the Dark Shadow from Space 146 5.5 Impact on the General Theory of Relativity 149 6. QUASARS AND GALACTIC NUCLEI 153 6.1 The Host Galaxies of Quasars 157 6.2 The Active Nuclei of Other Galaxies 161 6.3 Superluminal Motion 168 6.4 The Supermassive Black Hole Menagerie 174 6.5 Future Horizons 177 REFERENCES 179 INDEX 183