How Did the First Stars and Galaxies Form?

How Did the First Stars and Galaxies Form?

ABRAHAM LOEB
Copyright Date: 2010
Edition: STU - Student edition
Pages: 216
https://www.jstor.org/stable/j.ctt7rgcd
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    How Did the First Stars and Galaxies Form?
    Book Description:

    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 cosmologyCovers all the basic conceptsGives an overview of the gravitational growth of perturbations in an expanding universeExplains the process of reionizationDescribes the observational methods used to detect the earliest galaxies

    eISBN: 978-1-4008-3406-8
    Subjects: Astronomy, Physics

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-x)
  3. PREFACE
    (pp. xi-xvi)
    A. L.
  4. 1 PROLOGUE: THE BIG PICTURE
    (pp. 1-7)

    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...

  5. 2 STANDARD COSMOLOGICAL MODEL
    (pp. 8-34)

    In 1915 Einstein came up with the general theory of relativity. He was inspired by the fact that all objects follow the same trajectories under the influence of gravity (the so-called equivalence principle, which by now has been tested to better than one part in a trillion), and realized that this would be a natural result if space-time is curved under the influence of matter. He wrote down an equation describing how the distribution of matter (on one side of his equation) determines the curvature of space-time (on the other side of his equation). He then applied his equation to...

  6. 3 THE FIRST GAS CLOUDS
    (pp. 35-63)

    The initial conditions of the Universe can be summarized on a single sheet of paper. The small number of parameters that provide an accurate statistical description of these initial conditions are summarized in table 3.1. However, thousands of books in libraries throughout the world cannot summarize the complexities of galaxies, stars, planets, life, and intelligent life in the present-day Universe. If we feed the simple initial cosmic conditions into a gigantic computer simulation incorporating the known laws of physics, we should be able to reproduce all the complexity that emerged out of the simple early Universe. Hence, all the information...

  7. 4 THE FIRST STARS AND BLACK HOLES
    (pp. 64-94)

    There are two branches of theoretical research in cosmology. One considers the global properties of the Universe and the physical principles that govern it. As more data come in, our knowledge of the initial conditions as well as the underlying cosmological parameters gets refined with higher and higher precision. The second branch focuses on the formation of observable (luminous) objects out of the cosmic gas, including the stars and black holes in galaxies. Here, as more data come in, the models get more complex and the modelers understand more clearly why their previous analysis oversimplified the underlying processes. Theorists who...

  8. 5 THE REIONIZATION OF COSMIC HYDROGEN BY THE FIRST GALAXIES
    (pp. 95-115)

    The cosmic microwave background (CMB) indicates that hydrogen atoms formed 400 thousand years after the Big Bang, as soon as the gas cooled below 3,000K as a result of cosmological expansion. Observations of the spectra of early galaxies, quasars, and gamma-ray bursts indicate that less than a billion years later the same gas underwent a wrenching transition from atoms back to their constituent protons and electrons in a process known as reionization. Indeed, the bulk of the Universe’s ordinary matter today is in the form of free electrons and protons, located deep in intergalactic space. The free electrons have other...

  9. 6 OBSERVING THE FIRST GALAXIES
    (pp. 116-135)

    A couple of years ago, my family and I visited the remote island of Tasmania off the coast of Australia, known for its unspoiled natural environment. Upon our arrival at a secluded lodge near the beautiful Cradle Mountain reserve, I discovered there was no internet connectivity. When night settled in, I had a few hours to spare—the time I ordinarily use to answer e-mails and check the daily postings of papers on the astro-ph web archive. I stepped out of our cabin and looked around at the pristine sight of nature left to its own. The night was dark...

  10. 7 IMAGING THE DIFFUSE FOG OF COSMIC HYDROGEN
    (pp. 136-158)

    Hydrogen is the most abundant element in the Universe. It is also the simplest atom possible, containing a proton and an electron held together by their mutual electric attraction. Because of its simplicity, the detailed understanding of the hydrogen atom structure played an important role in the development of quantum mechanics.

    Since the lifetime of energy levels with principal quantum number 𝑛 greater than 1 is far shorter than the typical time it takes to excite them in the rarefied environments of the Universe, hydrogen is commonly found to be in its ground state (lowest energy level) with$n = 1$. This...

  11. 8 EPILOGUE: FROM OUR GALAXY’S PAST TO ITS FUTURE
    (pp. 159-170)

    The previous chapters have been dedicated to the distant past of our cosmic ancestry, when the building blocks of the Milky Way galaxy were assembled in the form of the first galaxies. The laws of physics also allow us to forecast how our Galaxy and its environment will likely change in the future. Our cosmic perspective would be incomplete without a glimpse into this future.

    Previous generations of scholars have occasionally wondered about the long-term future of the Universe or in Biblical Hebrew, the forecast foracharit hayamim(“the end of times”). For the first time in history, we now...

  12. APPENDIX: USEFUL NUMBERS
    (pp. 171-172)
  13. NOTES
    (pp. 173-180)
  14. RECOMMENDED FURTHER READING
    (pp. 181-182)
  15. GLOSSARY
    (pp. 183-188)
  16. INDEX
    (pp. 189-193)