spacetoday.net: Methane detected on exoplanet

Posted: Thu, Mar 20, 2008, 7:41 AM ET (1141 GMT)
HD 189733b exoplanet illustration (NASA/ESA)

Astronomers have detected evidence of methane in the atmosphere of an extrasolar planet, the first organic molecule discovered on a planet outside our solar system. In a paper published in this week's issue of the journal Nature, astronomers reported that they had detected methane in the atmosphere of HD 189733b, a planet closely orbiting a star 63 light-years from the Earth. The discovery was made by the Hubble Space Telescope, which observed the planet as it transited in front of its parent star as seen from Earth; the light from the star passed through the planet's atmosphere, creating absorption lines in the spectrum that astronomers linked to methane. The same data also confirmed the presence of water in the planet's atmosphere, a discovery announced last year from observations by the Spitzer Space Telescope. Astronomers found more methane in the planet's atmosphere than previous models predicted for so-called "hot Jupiters", gas giants that orbit very close to their stars.