Otherworldly images

This beautiful book is written by Ray Villard, news director of the Space Telescope Science Institute, with paintings by Lynette Cook (shiwn here), who as a space artist has few equals and no superiors. The photographs, many of them from the Hubble Space Telescope, have been carefully selected and excellently reproduced. There is a foreword by Geoffrey Marcy, one of the leaders in the search for extrasolar planets, and an afterword by Frank Drake, the real pioneer in this field of research.

The first chapters set the scene, giving a very good account of modern theories about the origin and development of the universe, together with a more detailed look at stellar evolution. This leads on to the book's main theme; the discovery and nature of planets orbiting other stars. It now seems surprising that the first of these, 51 Pegasi b, was detected less than 20 years ago. Since then, the total number of extrasolar planets has risen to more than 150, and more are being found almost every month. It has become clear that many stars do have planetary systems, and it is hard to doubt that many of these are suitable for life - but as yet we have no proof that life will appear wherever conditions are tolerable. Moreover, planets of other stars are detected by indirect methods, and we are only just starting to obtain visual confirmation.

When discussing extraterrestrial life, it is easy to speculate, and these writers are certainly not afraid to do so, but their speculations are always based firmly on 21st-century knowledge. For example, there is nothing outrageous in the eye-catching painting of the surface of Europa, Jupiter's second satellite. Europa has a cracked, icy crust that probably overlies an ocean of water; how can we be sure that this sunless sea is sterile? "In the not-too-distant future we could be looking at samples of organisms spawned a half billion miles away." Then there is Titan, with its thick, cloudy atmosphere; we know more about it now than we did when the text was written, thanks to the Cassini space mission, but we can visualise what Titan will be like 5 billion years in the future, when the Sun has become a giant red star: "Titan will have liquid lakes and pools to incubate life, in a brief replay of what happened 10 billion years ago in the now incinerated inner Solar System." The painting may turn out to be uncannily accurate, though Earth will long since have been destroyed.

Far away in space, speculation is endless; we can imagine the view from a world near the Siamese Squid Nebula, or the yellow star Alpha Centauri looming over the arid desert of one of its planets, or the strange scene from a planet moving in the "habitable zone" of a pair of red dwarf stars.

This is reasonable, but in the end sections of the book there is a hint of pure science fiction - for instance, a fascinating picture of "an intelligent light being" made up not of matter, but of "photons or other forms of energy". Yet science fiction has a habit of turning into science fact, and we cannot rule out such speculations completely.

One criticism must be that here and there we find theories presented as established facts; for instance, not all authorities agree that the dinosaurs were wiped out by the impact of an asteroid or meteorite, and we still cannot be definite about the eventual fate of the universe, but this is a minor point and opinions are always bound to differ.

This is an ideal coffee-table book, but it is more than that, because it contains so much sound science. The presentation is excellent and the publishers are to be congratulated on keeping the price down to an acceptable level. Make haste to add it to your library.

Sir Patrick Moore is an astronomer whose Atlas of the Universe is out now.