Astronomers have detected the organic molecule methane in the atmosphere of an extrasolar planet for the first time and have confirmed earlier observations of water vapor. Alas, the findings don’t come close to suggesting that life has emerged on this other world, but they do contribute to a growing body of data about planetary evolution outside our own solar system. Over about 15 years, astronomers have discovered 277 planets orbiting other stars. They have relied on two techniques, nicknamed “wobble” and “dip,” which infer the mass and position of far-off planets from the effect they have on the motion and brightness of their stars. Astronomers can learn a bit more when a planet transits between its star and Earth: Changes in a star’s light spectrum may reveal chemicals in a planet’s atmosphere.
Using this technique, researchers report in tomorrow’s issue of Nature that a 40-minute gaze with the Hubble Space Telescope last May has revealed methane in the atmosphere of HD 189733b, a Jupiter-size planet orbiting close to its very bright parent star located 63 light-years away. The observation also confirmed last year’s discovery by the Spitzer Space Telescope of water vapor in the planet’s atmosphere.