Author: Ray Jayawardhana
Publisher: Princeton University Press
Price: £16.95 (hardback)
Isbn: 9780691142548

In 1991, astronomers announced that they had unambiguously discovered the first planet outside the nine (poor Pluto had not then been demoted) in our solar system. The planet orbited a pulsar – a rotating, decayed star that sends out a regular beam of radiation, rather like a lighthouse sends out light. Changes in the pattern of radiation led astro­nomers to infer the existence of a planet of 10 times the mass of Earth orbiting the pulsar.

Four years later, astronomers revealed definitive evidence of a planet orbiting a normal star other than the Sun – but these were gas giants, rather akin to supersized Jupiters. ‘Super-Earths’ followed in 2005, beginning with a planet at least 7.5 times the mass of Earth orbiting the red dwarf Gliese 876, about 15 light years distant. At the time of writing, astronomers have discovered 531 exoplanets orbiting 445 stars, excluding pulsars (see http://1.usa.gov/4dFvs9 for the latest tally). It’s a fascinating story, which Ray Jayawardhana, a planet hunter, Canadian professor of astronomy and science writer, tells with panache, enthusiasm and insight.

Strange New Worlds is populist and rich in anecdote. For example, the temperature difference (1400 degrees Celsius) between the night and day sides of upsilon Andromedæ b is “equivalent to leaping into a volcano”. (Last October, scientists also reported the intriguing, and unexplained, finding that the hottest place on this ‘hot Jupiter’ isn’t directly under the red dwarf’s glare.)

Jayawardhana further enliv­ens his book with biographical vignettes, which help make Strange New Worlds accessible for the ‘general’ reader. For example, William Huggins’s spectroscopic studies showed that nebulæ and galaxies – then often little more than fuzzy smears seen through telescopes – consisted of gas and stars respectively. Huggins wasn’t a professional astronomer: he was a retired Victorian silk merchant inspired by a lecturing scientist. Amateurs continue to make important contributions to astro­nomy and it would be an apposite tribute to this excellent book if Jayawardhana inspires others to continue the tradition.

Jayawardhana covers too much ground to review extensively the evidence supporting each comm­ent. Nevertheless, on a few occas­ions, I felt the ‘average’ reader would have benefited from more discussion and greater detail. For example, in the early 1960s, ‘wobbles’ in Bernard’s star led some astronomers to infer the presence of a planet with 1.6 times the mass of Jupiter. Arguments raged, Jayawardhana notes, as to whether the wobble arose from “spurious effects” in the telescope or variations in the photographic plate and by the mid-1980s most astronomers “had given up on the planet’s existence”. But why did the argument persist for years? A discussion could exemplify the problems facing scientists when deciding whether a finding is an observational artefact, an issue the ‘general’ public should bear in mind – technological improvements notwithstanding – when reading about astronomical and other scientific advances in the popular media today.

Similarly, Jayawardhana comm­ents that “some would say that astrobiology had a dubious debut” when researchers announced that the now iconic Martian meteorite ALH84001 “contained fossils and other evid­ence of nano­bacteria – a claim now disputed by many scientists”. A few more paragraphs discussion would help readers appreciate why “many scientists” dispute the claim – especially as ALH84001 captured headlines around the world and popular documentaries and feat­ures still refer to the meteorite. Readers could benefit from a more detailed discussion about what would constitute a signal of alien life, especially as scientists can’t agree on how to define life on Earth. (I addressed this issue – arguably the most vexed in biology in 2008 – in a feature for a European Molecular Biological Organisation journal: http://bit.ly/l32ITw). Jayawardhana’s a clear and insightful writer – so there’s no risk that a more detailed discussion would have lost a ‘general’ reader or they’d become bogged down in the detail.

Despite these minor – and that’s what they are – caveats, we should applaud and welcome Jayawardhana’s ability to bring the often esoteric realm of exoplanet astronomy within the grasp of the average Discovery Channel viewer. Strange New Worlds reminded me of an article in New Scientist or a ‘quality’ paper: a readable introduction to one of the most provocative and thought-provoking areas in science that requires no background in either astronomy or science more generally. Very highly recommended.