How Did the First Stars and Galaxies Form? (Princeton Frontiers in Physics) - Softcover

Loeb, Abraham

Softcover

ISBN 10: 0691145164 ISBN 13: 9780691145167

Verlag: Princeton University Press, 2010

Inhaltsangabe

A concise introduction to cosmology and how light first emerged in the universe

Though astrophysicists have developed a theoretical framework for understanding how the first stars and galaxies formed, only now are we able to begin testing those theories with actual observations of the very distant, early universe. We are entering a new and exciting era of discovery that will advance the frontiers of knowledge, and this book couldn't be more timely. It covers all the basic concepts in cosmology, drawing on insights from an astronomer who has pioneered much of this research over the past two decades.

Abraham Loeb starts from first principles, tracing the theoretical foundations of cosmology and carefully explaining the physics behind them. Topics include the gravitational growth of perturbations in an expanding universe, the abundance and properties of dark matter halos and galaxies, reionization, the observational methods used to detect the earliest galaxies and probe the diffuse gas between them—and much more.

Cosmology seeks to solve the fundamental mystery of our cosmic origins. This book offers a succinct and accessible primer at a time when breathtaking technological advances promise a wealth of new observational data on the first stars and galaxies.

• Provides a concise introduction to cosmology
• Covers all the basic concepts
• Gives an overview of the gravitational growth of perturbations in an expanding universe
• Explains the process of reionization
• Describes the observational methods used to detect the earliest galaxies

Über diesen Titel

Über die Autorin bzw. den Autor

Abraham Loeb is professor of astronomy and director of the Institute for Theory and Computation at Harvard University.

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"Abraham Loeb, a leading figure in exploring the emergence of first galaxies and stars, introduces the astrophysics of the first billion years. With a strong emphasis on the underlying physics, this book will be an essential starting point for both observers and theorists who are interested in this rapidly evolving area of cosmology."--David Spergel, Princeton University

"A lucid, concise account of our current understanding of how light burst from darkness when the first stars and galaxies formed early in the expansion of the universe. Starting from basic physical principles, Loeb describes the physical processes that shaped the evolution of the universe, how they led to the formation of the first black holes, quasars, and gamma-ray bursts, and how upcoming observations will test these ideas."--Christopher F. McKee, University of California, Berkeley

"This is a lively, well-written book. Loeb is an excellent writer and talented instructor who is also internationally recognized in the research community. The topic at hand--the first stars and galaxies--is truly an exciting frontier for which Loeb and his collaborators have developed much of the theoretical framework, and for which the observational possibilities are rapidly developing. The timing of this book couldn't be better."--Richard S. Ellis, California Institute of Technology

"This is an extremely good book. Loeb guides readers through the early, formative history of the universe. He does not shy away from key calculations, but always tries to make things as simple as possible. His style is truly engaging, with a constant eye on the big picture. It makes for a thrilling read. Indeed, I found it difficult to put down."--Volker Bromm, University of Texas, Austin

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HOW DID THE First Stars and Galaxies Form?

By ABRAHAM LOEB

PRINCETON UNIVERSITY PRESS

Copyright © 2010 Princeton University Press
All right reserved.
ISBN: 978-0-691-14516-7

Contents

PREFACE.........................................................................xi1 Prologue: The Big Picture.....................................................12 Standard Cosmological Model...................................................83 The First Gas Clouds..........................................................354 The First Stars and Black Holes...............................................645 The Reionization of Cosmic Hydrogen by the First Galaxies.....................956 Observing the First Galaxies..................................................1167 Imaging the Diffuse Fog of Cosmic Hydrogen....................................1368 Epilogue: From Our Galaxy's Past to Its Future................................159APPENDIX: USEFUL NUMBERS........................................................171NOTES...........................................................................173RECOMMENDED FURTHER READING.....................................................181GLOSSARY........................................................................183INDEX...........................................................................189

Chapter One

PROLOGUE: THE BIG PICTURE

1.1 In the Beginning

As the Universe expands, galaxies get separated from one another, and the average density of matter over a large volume of space is reduced. If we imagine playing the cosmic movie in reverse and tracing this evolution backward in time, we can infer that there must have been an instant when the density of matter was infinite. This moment in time is the "Big Bang," before which we cannot reliably extrapolate our history. But even before we get all the way back to the Big Bang, there must have been a time when stars like our Sun and galaxies like our Milky Way did not exist, because the Universe was denser than they are. If so, how and when did the first stars and galaxies form?

Primitive versions of this question were considered by humans for thousands of years, long before it was realized that the Universe expands. Religious and philosophical texts attempted to provide a sketch of the big picture from which people could derive the answer. In retrospect, these attempts appear heroic in view of the scarcity of scientific data about the Universe prior to the twentieth century. To appreciate the progress made over the past century, consider, for example, the biblical story of Genesis. The opening chapter of the Bible asserts the following sequence of events: first, the Universe was created, then light was separated from darkness, water was separated from the sky, continents were separated from water, vegetation appeared spontaneously, stars formed, life emerged, and finally humans appeared on the scene. Instead, the modern scientific order of events begins with the Big Bang, followed by an early period in which light (radiation) dominated and then a longer period dominated by matter, leading to the appearance of stars, planets, life on Earth, and eventually humans. Interestingly, the starting and end points of both versions are the same.

1.2 Observing the Story of Genesis

Cosmology is by now a mature empirical science. We are privileged to live in a time when the story of genesis (how the Universe started and developed) can be critically explored by direct observations. Because of the finite time it takes light to travel to us from distant sources, we can see images of the Universe when it was younger by looking deep into space through powerful telescopes.

Existing data sets include an image of the Universe when it was 400 thousand years old (in the form of the cosmic microwave background in figure 1.1), as well as images of individual galaxies when the Universe was older than a billion years. But there is a serious challenge: in between these two epochs was a period when the Universe was dark, stars had not yet formed, and the cosmic microwave background no longer traced the distribution of matter. And this is precisely the most interesting period, when the primordial soup evolved into the rich zoo of objects we now see. How can astronomers see this dark yet crucial time?

The situation is similar to having a photo album of a person that begins with the first ultrasound image of him or her as an unborn baby and then skips to some additional photos of his or her years as teenager and adult. The late photos do not simply show a scaled-up version of the first image. We are currently searching for the missing pages of the cosmic photo album that will tell us how the Universe evolved during its infancy to eventually make galaxies like our own Milky Way.

The observers are moving ahead along several fronts. The first involves the construction of large infrared telescopes on the ground and in space that will provide us with new (although rather expensive!) photos of galaxies in the Universe at intermediate ages. Current plans include ground-based telescopes which are 24–42 m in diameter, and NASA's successor to the Hubble Space Telescope, the James Webb Space Telescope. In addition, several observational groups around the globe are constructing radio arrays that will be capable of mapping the three-dimensional distribution of cosmic hydrogen left over from the Big Bang in the infant Universe. These arrays are aiming to detect the long-wavelength (redshifted 21-cm) radio emission from hydrogen atoms. Coincidentally, this long wavelength (or low frequency) overlaps with the band used for radio and television broadcasting, and so these telescopes include arrays of regular radio antennas that one can find in electronics stores. These antennas will reveal how the clumpy distribution of neutral hydrogen evolved with cosmic time. By the time the Universe was a few hundreds of millions of years old, the hydrogen distribution had been punched with holes like swiss cheese. These holes were created by the ultraviolet radiation from the first galaxies and black holes, which ionized the cosmic hydrogen in their vicinity.

Theoretical research has focused in recent years on predicting the signals expected from the above instruments and on providing motivation for these ambitious observational projects. In the subsequent chapters of this book, I will describe the theoretical predictions as well as the observational programs planned for testing them. Scientists operate similarly to detectives: they steadily revise their understanding as they collect new information until their model appears consistent with all existing evidence. Their work is exciting as long as it is incomplete.

At a young age I was attracted to philosophy because it addresses the most fundamental questions we face in life. As I matured to an adult, I realized that science has the benefit of formulating a subset of those questions that we can make steady progress on answering, using experimental evidence as a guide.

1.3 Practical Benefits from the Big Picture

I get paid to think about the sky. One might naively regard such an occupation as carrying no practical significance. If an engineer underestimates the strain on a bridge, the bridge may collapse and harm innocent people. But if I calculate incorrectly the evolution of galaxies, these mistakes bear no immediate consequence for the daily life of other people. Is this really the case?

The same engineer who designs bridges would be the first to correct this naive misconception. Newton...

Details zur Ausgabe

• Verlag: Princeton University Press
• Erscheinungsdatum: 2010
• Sprache: Englisch
• ISBN 10: 0691145164
• ISBN 13: 9780691145167
• Einband: Taschenbuch
• Anzahl der Seiten: 210
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar