Astronomers have detected water in the atmosphere of a planet outside our solar system for the first time. Using a combination of previously published Hubble Space Telescope measurements and new theoretical models, they found strong evidence for water absorption in the atmosphere of the extrasolar planet HD209458b. HD209458b is a world well-known among planet hunters. In 1999, it became the first planet to be directly observed around a normal star outside our solar system and, a few years later, was the first exoplanet confirmed to have oxygen and carbon in its atmosphere. HD209458b is separated from its star by only 7 million kilometres – about 100 times closer than Jupiter is to our Sun – and is so hot scientists think it is losing about 10.000 tons of material every second as vented gas.

Water Identified in Extrasolar Planet Atmosphere (PDF; 14 KB)

T. S. Barman: Identification of Absorption Features in an Extrasolar Planet Atmosphere