Signs of water on far-away planet
Updated on 11 December 2008
Clear signs of water have been found in the atmosphere of a giant hot planet orbiting a star beyond the Solar System.
Although the "hot Jupiter" is highly unlikely to support life, similar techniques may one day be used to identify habitable Earth-like planets in far-away star systems.
Scientists made the discovery by analysing the light from the star and planet combined, and from the star alone with the planet passing behind it. Subtracting one from the other isolated the planet's light contribution.
Averaging the results of 10 such observations showed a pattern consistent with light being absorbed by water vapour.
Previous evidence of water in the atmospheres of extra-solar planets has not been clear-cut, but the new findings are said to be unequivocal.
The team of astronomers led by Dr Carl Grillmair, from the California Institute of Technology at Pasadena, US, wrote in the journal Nature: "We find... discrete spectral features that are characteristic of strong absorption by water vapour."
Hubble Space Telescope astronomers have already announced finding carbon dioxide on the planet, known as HD 189733b.
The new observations were made using the Spitzer Space Telescope which focuses on infrared light.
The planet, which is 63 light years away, hugs its parent star closely unlike the four gas giants which orbit the sun, Jupiter, Saturn, Neptune and Uranus.
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