Technology & Science

Water identified in distant gas giant's atmosphere

British astronomers have found evidence of water in the atmosphere of a gas giant 64 light years from Earth, the first discovery of water in an extrasolar planet, they say.

British astronomers have found evidence of water in the atmosphere of a gas giant 64 light years from Earth, the first discovery of water in an extrasolar planet, they say.

Researchers at University College London (UCL) found that when theplanet HD 189733b passes in front of its sun, "it absorbs starlight in a way that can only be explained by the presence of water vapour in its atmosphere," they said in a release Wednesday.

They used data from an orbital telescope to measure wavelengths in the infrared spectrum that demonstrated the presence of water in the planet, which orbits a star in the constellation Vulpecula the Fox.

The discovery is a step towards the "'holy grail" for the researchers seeking an Earth-like planet with water, said Giovanna Tinetti, lead researcher and a member of UCL's department of physicsand astronomy.

"When it happens, that discovery will provide real evidence that planets outside our solar system might harbour life."

HD 189733b is about 15 per cent bigger than Jupiter and more than 30 times closer to its star than the Earth is to the sun.

That makes it extremely hot, so the water is not a liquid.

"It is not even steam; it is in thegaseous form, much like carbon dioxide, nitrogen or methane," said Bob Barber, also from UCL's department of physicsand astronomy.

Barber and UCL colleague Prof. Jonathan Tennyson useddata they generated by computer to identify water in the infrared spectrum of photos taken by NASA's Spitzer Earth-orbiting telescope. Their datais the most complete and accurate list of the spectral features due to hot water vapour, Barbersaid.

Theirresearchproduced a satisfactory model of the atmosphere of HD 189733b and has been used to identify water in other bodies in space, including comets, brown dwarfs, red giantsand sun spots.

The research was published in the July 12 edition of Nature.