Water on the planet HD 189733b

Scientists report the first conclusive discovery of the presence of water vapour in the atmosphere of a planet beyond our Solar System.

Infrared analysis of this gas giant’s transit across its parent star provided the breakthrough. The planet HD 189733b lies 63 light-years away, in the constellation Vulpecula.

Although, being a gas giant, the planet is an unlikely candidate in the search for life, these results increase hopes for the detection of water on other rocky planets, which astronomers hope to discover in the near future.

source:
http://www.esa.int/esaCP/SEMBDZI2O3F_index_0.html

'Clear Signs of Water' on Distant Planet
Scientists had previously looked for signs of water on HD 189733b but failed to find any. At the time, they suspected the water might be hidden beneath a thick layer of silicate clouds.

Tinetti and her team offer a different explanation. They hypothesize that unlike Earth, where the atmospheric temperature cools with altitude, the temperature of HD 189733b's atmosphere is uniform over a range of altitudes.

In the new study, the researchers observed HD 189733b as it passed in front of, or "transited," its parent star. Using Spitzer's infrared camera, the team analyzed light that was emitted from the interior of the parent star and which passed through the planet's atmosphere on its way to Earth. In this case, absorption occurs because of the temperature difference that exists between the star's atmosphere and that of the planet.

The researchers found that the planet absorbed starlight in such a way that could only be explained by the presence of water vapor in its atmosphere.
http://www.space.com/scienceastronomy/070711_water_planet.html

http://en.wikipedia.org/wiki/HD_189733b