Friedmann-Lemaître-Robertson-Walker (FLRW) metric
Astrophysics in a nutshell
``Astrophysics in a nutshell'' is the winner of the American Astronomical Society's Chambliss Award. It has become the text of choice in astrophysics courses at top universities in North America and beyond. The new, extended and fully updated second edition contains a new chapter on extrasolar planets, a greatly expanded chapter on the interstellar medium, fully updated facts and figures on all subjects, from the observed properties of white dwarfs to the latest results from precision cosmology, and additional instructive problem sets.NEWLINENEWLINEThe book is a brief but thorough introduction to the observational data and theoretical concepts underlying modern astronomy. It covers the essentials of modern astrophysics, emphasizing the common physical principles that govern astronomical phenomena. It shows the interplay between theory and observation -- while also introducing subjects at the forefront of modern research, including black holes, dark matter, dark energy, and gravitational lensing.NEWLINENEWLINEThe book uses simple, short, and clear derivations of physical results. It trains students in the essential skills of order of magnitude analysis. The text assumes familiarity with differential equations, classical and quantum mechanics, special relativity, theory of waves, statistical mechanics, and thermodynamics. The author excluded from the book almost all descriptions of historical developments of the various astrophysical topics. He presented the topics concisely, as they are understood today.NEWLINENEWLINEIn addition to serving as a course textbook, ``Astrophysics in a nutshell'' is an ideal review for a qualifying exam and a handy reference for teachers and researchers. In detail, the book consists of ten chapters. It starts with Chapter 1 on observational astrophysical techniques, considers stars and stellar physics, extrasolar planets, the Milky Way and other galaxies, basic cosmological observations, and ends with tests and probes of the Big Bang cosmology.NEWLINENEWLINEAstrophysical discoveries and quantifications are the products of observations, the techniques of which are the topic of Chapter 1. With the exceptions of neutrinos, cosmic rays and gravitational waves, astronomical objects are almost always observed by detecting and measuring electromagnetic radiation using a telescope. The larger the aperture of the telescope, the more photons per unit time may be detected. Hence, fainter astronomical objects may be detected. Today, the largest visible-light telescopes have primary mirrors with a size of 10 m. Chapter 1 discusses sketches of telescopes with different camera-detector combinations. The importance of the angular resolution and the exposure time of an observation are explained. Photometry, spectroscopy and polarimetry are briefly introduced.NEWLINENEWLINEIn Chapter 2, some of the basic observed properties of stars, their spectra, temperatures, emitted power, and masses, and the relations between these properties are examined. The blackbody radiation is reviewed. Finally, the Hertzsprung-Russel diagram is discussed, which shows stellar luminosity as function of effective temperature.NEWLINENEWLINEIn Chapter 3, the reader obtains a physical understanding of main-sequence stars and of their properties as outlined in Chapter 2. As the Sun ist the nearest and best studied star, and its properties provide useful standards to which other stars can be compared, the hydrostatic equilibrium model of the Sun is explained in detail. It consists of four differential equations of first order, three additional functions connecting pressure, opacity, and energy production rate of the plasma with its temperature, mass density and chemical composition.NEWLINENEWLINEBut, because of nuclear reactions and convection processes, stars are not in equilibrium. For instance, at some point, the hydrogen in a star's core will be largely used up by fusion processes, and the star loses the energy source that produces pressure, the gradient of which supports the star against a gravitational collapse. Thus, it is unavoidable that stars evolve with the time. In Chapter 4, various processes are discussed that stars of different masses undergo after the main sequence. The properties of their compact remnants, of white dwarfs, neutron stars, and black holes, are explained. Further, phenomena are studied, which occur when such compact objects accrete material from a companion star in a binary pair.NEWLINENEWLINEMuch of the baryonic matter in the Universe is distributed between the stars. This interstellar medium (ISM) consists of molecular, atomic and ionized gases, highly energetic particles called cosmic rays, and solid particles of dust. In Chapter 5, the molecular gas phase is of particular interest, as it contributes, under some conditions, to the formation of a new generation of stars. Chapter 5 focuses on the ISM, particularly in star-forming regions. Some of the properties of young stellar populations, the main physical processes operating in the ISM around newly formed stars, and the observable consequences of those processes are briefly surveyed. Then, the physics of shock waves is explored. It is explained, how cosmic rays are accelerated in shock waves.NEWLINENEWLINERecently, it was concluded, that planets around stars other than the Sun, i.e. extrasolar planets, are a common phenomenon. Planets are thought to be formed as a by-product of star formation, normally they orbit a star. Contrary to stars, which are supported against a collapse by thermal and radiative pressure gradients, or to white dwarfs, neutron stars, and brown dwarfs, which are supported by degeneracy pressure, planets have so small masses that they are supported by electrostatic forces. Chapter 6 examines the main observational methods, which are used to detect and to characterize extrasolar planets. The current picture of planetary-occurrence rates and planetary properties, as well as the current theory of planet formation and evolution are reviewed. Habitability and further searches for signs of life on extrasolar planets are also briefly discussed.NEWLINENEWLINEGalaxies are concentrations of \(10^7\) to \(10^{11}\) stars. They are essentially the only places where stars exist. The Sun is a star in the Milky Way, a large spiral galaxy. Chapter 7 examines the properties of the Milky Way, of other galaxies, and of systems of galaxies. Here also the possible nature and some forms of dark matter are considered -- and recently studied modified physics.NEWLINENEWLINEHaving dealt with progressively larger structures in the previous chapters, Chapter 8 reviews the basic observational facts that need to be accounted for by any theory of cosmology, i.e.\ any attempt to describe the nature, history, and future of the Universe as a whole. The chapter starts with an introduction of some of the main methods to measure distances of nearby stars up to galaxy cluster distances of about 1 Gpc, and continues with the discussion of Hubble's law, the determination of the age of the Universe by cosmic clocks, and the isotropy of the Universe.NEWLINENEWLINEChapter 9 deals with the Big Bang cosmology. It introduces the Friedmann-Lemaître-Robertson-Walker (FLRW) metric and the Friedmann equations of cosmology. These equations are two coupled differential equations for the three unknown time-dependent functions pressure, mass-energy density and scale factor of the Universe expansion. Solving the Friedmann equations for the scale factor can result into a description of the history and future of the Universe. Here, solutions for matter- and radiation-dominated Universes are derived. Further, the cosmological constant \(\Lambda\), introduced by Einstein, is discussed, which describes a repulsive force counteracting the gravity. Recently, it is believed that a \(\Lambda\)-like term is, in fact, required to describe the dynamics of our Universe. The \(\Lambda\)-like term is referred to the so-called dark energy (vacuum energy), a very challenging unsolved problem.NEWLINENEWLINEIn the final Chapter 10, experimental predictions of the cosmological model developed in Chapter 9, and their observational verification, are reviewed. The tests concern the cosmological redshift (in the context of distances to type-1a supernovae, and baryon acoustic oscillations), the cosmic microwave background, and the nucleosynthesis of the light elements. Each of these tests also provides information on the particular parameters that describe our Universe. The chapter concludes with a brief discussion on the use of quasars and other distant objects as cosmological probes.NEWLINENEWLINE(The review is written using small abstracts of the chapters of the book.)
scientific article; zbMATH DE number 6557080