Bradley Carroll – An Introduction to Modern Astrophysics (Second edition)

Автор: Bradley Carroll
Название книги: An Introduction to Modern Astrophysics (Second edition)
Формат: PDF
Жанр: Астрономия
Страницы: 1479
Качество: Изначально компьютерное, E-book

Since the first edition of An Introduction to Modern Astrophysics and its abbreviated companion
text, An Introduction to Modern Stellar Astrophysics, first appeared in 1996, there
has been an incredible explosion in our knowledge of the heavens. It was just two months
before the printing of the first editions that Michel Mayor and Didier Queloz announced
the discovery of an extrasolar planet around 51 Pegasi, the first planet found orbiting a
main-sequence star. In the next eleven years, the number of known extrasolar planets has
grown to over 193. Not only do these discoveries shed new light on how stars and planetary
systems form, but they also inform us about formation and planetary evolution in our own
Solar System.
In addition, within the past decade important discoveries have been made of objects,
within our Solar System but beyond Pluto, that are similar in size to that diminutive planet.
In fact, one of the newly discovered Kuiper belt objects, currently referred to as 2003 UB313
(until the International Astronomical Union makes an official determination), appears to be
larger than Pluto, challenging our definition of what a planet is and how many planets our
Solar System is home to.
Explorations by robotic spacecraft and landers throughout our Solar System have also
yielded a tremendous amount of new information about our celestial neighborhood. The
armada of orbiters, along with the remarkable rovers, Spirit and Opportunity, have confirmed
that liquid water has existed on the surface of Mars in the past. We have also had robotic
emissaries visit Jupiter and Saturn, touch down on the surfaces of Titan and asteroids, crash
into cometary nuclei, and even return cometary dust to Earth.
Missions such as Swift have enabled us to close in on the solutions to the mysterious
gamma-ray bursts that were such an enigma at the time An Introduction to Modern Astrophysics
first appeared.We now know that one class of gamma-ray bursts is associated with
core-collapse supernovae and that the other class is probably associated with the merger of
two neutron stars, or a neutron star and a black hole, in a binary system.
Remarkably precise observations of the center of our Milky Way Galaxy and other
galaxies, since the publication of the first editions, have revealed that a great many, perhaps
most, spiral and large elliptical galaxies are home to one or more supermassive black holes
at their centers. It also appears likely that galactic mergers help to grow these monsters in
their centers. Furthermore, it now seems almost certain that supermassive black holes are the
central engines responsible for the exotic and remarkably energetic phenomena associated
with radio galaxies, Seyfert galaxies, blazars, and quasars.
The past decade has also witnessed the startling discovery that the expansion of the universe
is not slowing down but, rather, is actually accelerating! This remarkable observation
suggests that we currently live in a dark-energy-dominated universe, in which Einstein’s cosmological constant (once considered his “greatest blunder”) plays an important role
in our understanding of cosmology. Dark energy was not even imagined in cosmological
models at the time the first editions were published.
Indeed, since the publication of the first editions, cosmology has entered into a new era of
precision measurements.With the release of the remarkable data obtained by theWilkinson
Microwave Anisotropy Probe (WMAP), previously large uncertainties in the age of the
universe have been reduced to less than 2% (13.7 ± 0.2 Gyr). At the same time, stellar
evolution theory and observations have led to the determination that the ages of the oldest
globular clusters are in full agreement with the upper limit of the age of the universe.
We opened the preface to the first editions with the sentence “There has never been
a more exciting time to study modern astrophysics”; this has certainly been borne out in
the tremendous advances that have occurred over the past decade. It is also clear that this
incredible decade of discovery is only a prelude to further advances to come. Joining the
Hubble Space Telescope in its high-resolution study of the heavens have been the Chandra
X-ray Observatory and the Spitzer Infrared Space Telescope. From the ground, 8-m and
larger telescopes have also joined the search for new information about our remarkable
universe. Tremendously ambitious sky surveys have generated a previously unimagined
wealth of data that provide critically important statistical data sets; the Sloan Digital Sky
Survey, the Two-Micron All Sky Survey, the 2dF redshift survey, the Hubble Deep Fields
and Ultradeep Fields, and others have become indispensable tools for hosts of studies.We
also anticipate the first observations from new observatories and spacecraft, including the
high-altitude (5000 m) Atacama Large Millimeter Array and high-precision astrometric
missions such as Gaia and SIM PlanetQuest. Of course, studies of our own Solar System
also continue; just the day before this preface was written, the Mars Reconnaissance Orbiter
entered orbit around the red planet.
When the first editions were written, even theWorldWideWeb was in its infancy. Today
it is hard to imagine a world in which virtually any information you might want is only
a search engine and a mouse click away. With enormous data sets available online, along
with fully searchable journal and preprint archives, the ability to access critical information
very rapidly has been truly revolutionary.
Needless to say, a second edition of BOB (the “Big Orange Book,” as An Introduction
to Modern Astrophysics has come to be known by many students) and its associated text
is long overdue. In addition to an abbreviated version focusing on stellar astrophysics (An
Introduction to Modern Stellar Astrophysics), a second abbreviated version (An Introduction
to Modern Galactic Astrophysics and Cosmology) is being published.We are confident that
BOB and its smaller siblings will serve the needs of a range of introductory astrophysics
courses and that they will instill some of the excitement felt by the authors and hosts of
astronomers and astrophysicists worldwide.
We have switched from cgs to SI units in the second edition. Although we are personally
more comfortable quoting luminosities in ergs s−1 rather than watts, our students are not.
We do not want students to feel exasperated by a new system of units during their first
encounter with the concepts of modern astrophysics. However, we have retained the natural
units of parsecs and solar units (M and L) because they provide a comparative context
for numerical values. An appendix of unit conversions (see back endpapers) is included for those who delve into the professional literature and discover the world of angstroms, ergs,
and esu.
Our goal in writing these texts was to open the entire field of modern astrophysics to
you by using only the basic tools of physics. Nothing is more satisfying than appreciating
the drama of the universe through an understanding of its underlying physical principles.
The advantages of a mathematical approach to understanding the heavenly spectacle were
obvious to Plato, as manifested in his Epinomis:
Are you unaware that the true astronomer must be a person of great wisdom?
Hence there will be a need for several sciences. The first and most important
is that which treats of pure numbers. To those who pursue their studies in
the proper way, all geometric constructions, all systems of numbers, all duly
constituted melodic progressions, the single ordered scheme of all celestial
revolutions should disclose themselves. And, believe me, no one will ever
behold that spectacle without the studies we have described, and so be able to
boast that they have won it by an easy route.
Now, 24 centuries later, the application of a little physics and mathematics still leads to
deep insights.
These texts were also born of the frustration we encountered while teaching our juniorlevel
astrophysics course. Most of the available astronomy texts seemed more descriptive
than mathematical. Students who were learning about Schrödinger’s equation, partition
functions, and multipole expansions in other courses felt handicapped because their astrophysics
text did not take advantage of their physics background. It seemed a double shame to
us because a course in astrophysics offers students the unique opportunity of actually using
the physics they have learned to appreciate many of astronomy’s fascinating phenomena.
Furthermore, as a discipline, astrophysics draws on virtually every aspect of physics. Thus
astrophysics gives students the chance to review and extend their knowledge.
Anyone who has had an introductory calculus-based physics course is ready to understand
nearly all the major concepts of modern astrophysics. The amount of modern physics
covered in such a course varies widely, so we have included a chapter on the theory of
special relativity and one on quantum physics which will provide the necessary background
in these areas. Everything else in the text is self-contained and generously cross-referenced,
so you will not lose sight of the chain of reasoning that leads to some of the most astounding
ideas in all of science.1
Although we have attempted to be fairly rigorous, we have tended to favor the sort of
back-of-the-envelope calculation that uses a simple model of the system being studied.
The payoff-to-effort ratio is so high, yielding 80% of the understanding for 20% of the
effort, that these quick calculations should be a part of every astrophysicist’s toolkit. In
fact, while writing this book we were constantly surprised by the number of phenomena
that could be described in this way. Above all, we have tried to be honest with you; we
remained determined not to simplify the material beyond recognition. Stellar interiors, stellar atmospheres, general relativity, and cosmology—all are described with a depth that
is more satisfying than mere hand-waving description.
Computational astrophysics is today as fundamental to the advance in our understanding
of astronomy as observation and traditional theory, and so we have developed numerous
computer problems, as well as several complete codes, that are integrated with the text
material.You can calculate your own planetary orbits, compute observed features of binary
star systems, make your own models of stars, and reproduce the gravitational interactions
between galaxies. These codes favor simplicity over sophistication for pedagogical reasons;
you can easily expand on the conceptually transparent codes that we have provided.
Astrophysicists have traditionally led the way in large-scale computation and visualization,
and we have tried to provide a gentle introduction to this blend of science and art.
Instructors can use these texts to create courses tailored to their particular needs by
approaching the content as an astrophysical smorgasbord. By judiciously selecting topics,
we have used BOB to teach a semester-long course in stellar astrophysics. (Of course,
much was omitted from the first 18 chapters, but the text is designed to accommodate such
surgery.) Interested students have then gone on to take an additional course in cosmology.
On the other hand, using the entire text would nicely fill a year-long survey course (and then
some) covering all of modern astrophysics. To facilitate the selection of topics, as well as
identify important topics within sections, we have added subsection headings to the second
editions. Instructors may choose to skim, or even omit, subsections in accordance with their
own as well as their students’ interests—and thereby design a course to their liking.
An extensive website at http://www.aw-bc.com/astrophysics is associated with
these texts. It contains downloadable versions of the computer codes in various languages,
including Fortran, C++, and, in some cases, Java. There are also links to some of the
many important websites in astronomy. In addition, links are provided to public domain
images found in the texts, as well as to line art that can be used for instructor presentations.
Instructors may also obtain a detailed solutions manual directly from the publisher.
Throughout the process of the extensive revisions for the second editions, our editors have
maintained a positive and supportive attitude that has sustained us throughout. Although we
must have sorely tried their patience, Adam R. S. Black, Lothlórien Homet, Ashley Taylor
Anderson, Deb Greco, Stacie Kent, Shannon Tozier, and Carol Sawyer (at Techsetters) have
been truly wonderful to work with.