THERE are two ways of approaching astronomy. Either you congratulate the
scientific world on the huge amount of information it has amassed about the planets,
stars and galaxies. Or you revel in the challenge presented by a host of celestial
mysteries, confident that there is a mass of work still to be done before everything
has been sorted out鈥攁nd that there are plenty of reasons for employing more
astronomers and using bigger and better telescopes, spacecraft and computers.
Dina Prialnik鈥檚 An Introduction to the Theory of Stellar Structure and
Evolution (CUP, 拢15.95, ISBN 0521650658) lies in the first camp. Here
we have a first-class textbook that spells out in a clear and methodical way the
principles that underlie the life cycles of stars and the physics of their
interiors.
Prialnik explains how stars generate their energy, why the vast majority are
stable and why mass is the dominant characteristic that dictates when they
die鈥攚hether via the supernova towards the neutron star and black hole, or
the less exotic and more gentle journey through stellar variability towards a
common white dwarf. The host of student exercises in this book, plus the useful
worked answers, ensure that any dedicated physics or mathematics undergraduate
can, with some effort, understand what is going on.
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Unsolved Problems in Stellar Evolution, edited by Mario Livio (CUP,
拢55, ISBN 0521780918), takes the opposite tack. It鈥檚 a set of well-written
and accessible reviews assembled by the Baltimore-based Space Telescope Science
Institute. Mysteries abound. Why are so few massive stars formed? How does loss
of stellar mass slow down the spin? How does the differing metal content affect
a star鈥檚 lifestyle? Why is the mass of the most numerous stars only one-eighth
that of our Sun? What are the rates of the various fusion reactions in the Sun鈥檚
interior? Why do certain regions of space have more brown dwarf stars than
others? How does the evolution of binary stars differ from that of singles? The
list goes on.
Astronomers are explorers, a fact underlined by Paul Hodge in Higher than
Everest: An Adventurer鈥檚 Guide to the Solar System (CUP, 拢18.95, ISBN
0521651336). Instead of bombarding the reader with facts and familiar images,
Hodge encourages us to imagine ourselves out there actually climbing about on
the surfaces of planets and moons. Like many 鈥渟pace-age鈥� scientists, Hodge
laments the fact that it is 29 years since people have physically explored a
non-terrestrial landscape.
He takes his intrepid traveller on imaginary scrambles up the Solar System鈥檚
highest volcano (Olympus Mons, on Mars), dusty traverses of the lunar crater
Galileo, and chilling dives under the deepest ice floes (on Saturn鈥檚 moon
Europa). Each adventure is hypothetically possible with modern technology. He
compares cliff climbs on Jupiter鈥檚 moon Miranda with the ascent of the Eigerwand
in Switzerland. He stresses the similarities between South Africa鈥檚 Drakensberg
mountains and Io鈥檚 Mount Euboea. And throughout he emphasises the beauty and the
thrill of what鈥檚 still out there to be discovered.
On a more prosaic level, if you want a round-up on the space age, a superb
source鈥攏ow out in paperback鈥攊s the Encyclopedia of Planetary
Sciences (edited by James Shirley and Rhodes Fairbridge, Kluwer Academic,
$99, ISBN 0792367944). Two hundred eminent contributors tell you all they
know, without spending too much time dwelling on what they don鈥檛. It is divided
into 459 easily digestible, well referenced and commendably brief essays on
everything from achondrite meteorites and John Couch Adams to the Soviet Zond
interplanetary spacecraft and Fritz Zwicky, Swiss astronomer and expert on
supernova.