Ray Jayawardhana. Strange New Worlds – The Search for Alien Planets and Life Beyond Our Solar System. Princeton University Press, 2011 – Reviewed by David Simpson.

There is little doubt the discovery of tell-tale signs of life elsewhere in the universe, let alone the receipt of an indisputably alien radio signal, would have massive implications for mankind – the first sign that life is not unique to Earth.

This book takes us through the history of our quest for knowledge of the heavens, from Greek philosophers in the fifth century BC, through advances in astronomical observation methods, to the latest space telescopes. Finally it speculates a decade or more to the future, by when the author feels astronomers will probably have the means to detect the first signs of life elsewhere. It is not about SETI, ¬ the long-standing attempt to detect intelligent alien radio signals, but rather how incremental advances in telescopes now mean that, for the first time, we are able to detect planets orbiting distant stars – albeit planets much larger than Earth and inhospitable to life [as we know it, Jim] – and to infer something about their likely properties.

The title Strange New Worlds is perhaps a bit misleading as astronomers haven’t yet found any new worlds of the might-contain-life variety and those they have found are not strange in the wholly unexpected sense. They have detected an impressive number in the ‘almost certainly won’t contain life’ category, for example gas-giants like Jupiter, and rocky planets baking at 200 °C or more. Similarly misleading is the sub-title The Search for Alien Planets... hinting that astronomers are searching specifically for planets containing aliens, when they are not, and Life Beyond Our Solar System is last-chapter speculation about what future, more sensitive astronomical measurements might find. But I guess A History of Man’s Search for Exoplanets would probably not sell so well.

The subject’s chronology is presented in detail, is well referenced and gives credit to many of the main scientists involved. Their biographical stories are interesting too, although extending this to the scientists’ parents and even grandparents seems a bit much, as did the tedious information about who did a PhD under whom. I would have preferred the space to be used for a sentence or two here and there on the technical benefits of newer instruments, for example what was it about digital cameras and spectrographs that brought improved measurements? For non-astronomers like me the countless indecipherable alphanumeric strings of star identifiers were quite numbing but probably have to be there and were easily skipped.

The principles employed in detecting extrasolar planets are clearly explained, such as: measuring the tiny cyclic changes in the Doppler shift of light from a distant star – indicating the gravitation tug of an orbiting planet; ‘microlensing’¬ – looking at starlight as it is bent and amplified by the gravitational field of a large intervening object or; transit measurements – measuring the periodic changes in star brightness as it is eclipsed by an orbiting planet.

It is fascinating to appreciate the changes in scientific attitude towards the subject, from the 1980s when bothering to searching for extraterrestrial planets or even whether it was a legitimate part of astronomy was questioned, to today when vast sums of money are spent funding scientific teams exploring avenues in ‘astrobiology’. This includes, for example, working out what constitutes a biosignature – something that indicates the existence of living organisms.

Gripes aside, it is an interesting and well written book that doesn’t need much technical knowledge to be appreciated.

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