Extreme Stars at the Edge of Creation

By James Kaler
Published by Cambridge, 2001

Review by Dave Gordon

James Kaler is professor of astronomy at the University of Illinois. He has published more than 100 research papers, targeting his core research area: planetary nebulae. He has written articles for Sky and Telescope, Stardate and Scientific American. His other well-known book is titled "Stars and their Spectra", published by Cambridge 1997.

Extreme Stars is a generously illustrated hard cover peppered with recent Hubble Space Telescope photographic plates, tables, charts and diagrams. The centre section contains 16 high-gloss colour plates, including such gems as eta Carinae, the Ring-Tail Galaxy in Corvus and the famous Hubble Deep Field 100-hour exposure.

The remaining 228 pages are logically arranged into 10 enticing chapter titles, including "The Coolest Stars", "The Hottest Stars", "The Brightest Stars", "The Largest Stars", "The Smallest Stars", "The Youngest Stars", "The Oldest Stars" and closing with "The Strangest Stars".

The opening whistle is our very own Sun. He immediately satisfies his data-hungry readers with the most recent statistics of temperatures, mass, densities, etc. Here is a tasty morsel: "Shining with 4 x 10²⁶ watts, the equivalent of 4 million, million, million, million hundred-watt light bulbs, it releases the world’s annual energy production in one ten-millionth of a second – and it has been doing so for 4.6 billion years!"

This is by no means an easy bedtime read. For Dr Kaler whips nonchalantly from chemistry to physics, from Einstein to spectroscopy, from historical astronomy and back to astro-physics. But he does so with a style that is both sensible and unassuming.

It is worth noting that James Kaler bases most of this book’s content on the basis of understanding star’s spectra and the Hertzsprung-Russel diagram. For this reason, his early detailed and careful explanations of star-types, colours, temperatures and magnitudes leaves one in good stead for the remainder of the book.

In the chapter "the Coolest Stars", there is a fascinating section on carbon stars which launched me on a personal project to observe some of these blood-red wonders. We are treated to some delightful explanations of exotics such as Krüger 60, Wolf 360 and Gliese 229B.

In "The Hottest Stars", Kaler’s core research are, planetary nebulae, are given centre stage. The central stars of these enigmatic formations reach record surface temperatures approaching 200 000 Kelvin.

The chapter featuring the brightest stars sees Kaler contrast the differences between visual and photographic magnitudes. He then launches into a fascinating discussion on stars that display extraordinary variation, such as the famous eta Carinae. I particularly enjoyed his discussion of Wolf-Rayet stars, with their rather eccentric spectra.

The largest stars chapter is as engrossing as a Stephan King spine-chiller. Betelgeuse is 700 times the diameter of the Sun – extending halfway between the orbits of Mars and Jupiter. And so the chapter builds – from the mighty blasts of supernovae to the incredible crushing densities of Neutron stars and white dwarfs.

To touch on a bit of everything this book has to offer in such a short review would be an injustice to the author, who is clearly a master of his subject. It is difficult to find short-comings in this book. But I did find myself wishing for a few more lists of similarly categorised stars such as carbon stars, cataclysmic variables, the hottest stars, etc. Perhaps a reference appendix with co-ordinates of such objects wouldn’t have been misplaced.

In closing, Kaler doesn’t pull any punches. His penultimate colour plate is a famous Apollo Earth view in which he declares: "Home, our solid Earth, made mostly of the debris of supernovae" But his soft side prevails and his final colour plate is that of a mauve rose bathed in brilliant sunlight: "The grandeur of a living rose places the sun among the true wonders of the universe".