Water vapour detected on alien world

Water vapour has been found in the atmosphere of a Jupiter-like planet outside our solar system.

Planetary scientists had predicted that "hot Jupiters" - massive gas giants orbiting perilously close to their host stars - would have water vapour in their atmospheres. In April, astronomers claimed they had found some using the Hubble Space Telescope, but many dismissed the evidence as flawed.

Now Giovanna Tinetti of University College London and her colleagues have used the Spitzer Space Telescope to probe HD 189733b, a hot Jupiter orbiting a star just 63 light years from Earth. They studied starlight in three infrared bands centred around wavelengths of 3.6, 5.8 and 8 micrometres, and found that when the planet crossed the face of the star, the light dimmed in a manner consistent with the absorption of light by water vapour.

The team had predicted just such a dimming. "This is the first strong evidence of it," says team member Jean-Philippe Beaulieu of the Astrophysics Institute in Paris.

CREDIT: New Scientist magazine