PARIS — The quest to find another world that sustains life has been boosted by a technique that should let less expensive ground-based telescopes join the search, a study said on Wednesday. So far, more than 400 so-called exoplanets — planets that orbit stars other than the Sun — have been spotted since 1995, although none has been a rocky, watery world like our own. The key to finding the habitability of these worlds lies especially with spectroscopy, or the analysis of the spectrum of light reflected by the planet, which gives telltales about its atmosphere. Until now, such work has been the preserve of orbital telescopes, where viewing opportunities are strictly rationed because of the huge cost of the gadget. But astronomers in British and Germany say they have developed a technique in data analysis that should enable relatively small ground-based telescopes to take part in the hunt. In a paper published on Wednesday in the British journal Nature, the team were able to identify a ‘fluorescent’ form of methane in the upper atmosphere of an exoplanet 63 light years away. The target is HD 189733b, a gas giant closely orbiting a star […]