Sunquakes: Probing the Interior of the Sun.
J. B. Zirker.
xiv + 265 pp. The Johns Hopkins University
Press, 2003. $29.95.
In a sense, solar astronomy suffers from an image problem. Our Sun
remains, for the most part, as enigmatic as it was thousands of
years ago. Yet the general public, and even most astronomers, seldom
think about its mysteries. Solar physics is rarely mentioned in the
newspaper except on the occasion of eclipses or solar flares that
generate auroral displays. But now readers can get a sense of how
exciting the field can be from the remarkable book Sunquakes:
Probing the Interior of the Sun, by J. B. Zirker,
astronomer emeritus at the National Solar Observatory in Sunspot, Arizona.
The book's focus is the development of the relatively new scientific
discipline of helioseismology—the study of subtle vibrations
that we see on the surface of the Sun. Detection of these
oscillations in the early 1960s was a technical tour de force. It
required the measurement of extremely subtle Doppler shifts in
spectral lines, which signal wavelike motions of the solar surface.
Understanding the nature of these vibrations as acoustic
oscillations (organized sound waves) allowed scientists to use them
to probe, in detail, the structure and dynamics of the inside of the
Sun in much the same way that terrestrial seismology has revealed
the internal structure of the Earth. Sunquakes provides an
excellent, comprehensive overview of the history of the field, from
the early discoveries of the 1960s through the establishment of
current Earth-based and space-based helioseismology programs. Lucid
discussions of the scientific principles and challenges of the quest
to understand solar oscillations are interspersed with anecdotes
revealing the personalities involved.
I wish that such a book on solar astronomy had existed when I was a
graduate student and had the notion that solar astronomy was less
than thrilling. Luckily, I learned otherwise during a postdoc at
Yale from 1986 to 1989, where I helped model the rotating solar
interior, discovering firsthand the intellectual challenges of solar
physics. There I had the opportunity to meet many of the scientists
profiled in Sunquakes. Although I now study the seismology
of other stars, solar astronomy remains a strong interest of mine.
This book demonstrates how much a few dedicated individuals can
accomplish in a relatively short time. Helioseismology was developed
and continues to thrive through the cooperative efforts of
theorists, instrument builders and other highly motivated people.
Zirker does discuss some of the more contentious debates within the
field, in the process acknowledging the fierce competitiveness of
the researchers. More important, he makes the point that broad
cooperative collaboration can accelerate progress in a field and be
fun at the same time.
Helioseismology is a key tool for studying complex subjects such as
stellar convection and the origin of the solar magnetic field.
Discoveries by helioseismologists about the internal structure of
the Sun also eliminated the astronomical uncertainties in the
"solar neutrino problem" (why we detect far fewer
electron-flavored neutrinos than standard theory predicts are
emitted from the nuclear engine of the Sun) and helped focus efforts
to find the explanation in terms of particle physics.
Sunquakes is a remarkable book that conveys a true sense of
the excitement involved in the development of a new scientific
discipline. The main body of the text discusses the science with
accuracy and at a level appropriate for a general readership. Zirker
reserves more detailed discussions for chapter notes, which appear
at the end of the book and display the same ease of style and level
of precision as the main text. As is inevitable in such a book,
there are a few minor inaccuracies, but these should not detract
from the reader's enjoyment.
There may never be a "best time" to compile a story about
an active research area. By definition, such areas are fluid and
changing rapidly, so what seems to be the dominant paradigm at the
moment can be dramatically altered in short order. Given this,
Zirker has certainly captured the essence of helioseismology for the
present day. This book is a well-timed and capable recounting of the
birth and maturation of the field.—Steven Kawaler,
Physics, Iowa State University