Astronomers find water on extrasolar planet
Astronomers have found the best evidence yet of water on a planet beyond our Solar System. The planet, known as HD 189733b, is a Jupiter-like gas giant about 60 light-years away from Earth in the constellation of Vulpecula, the Fox. Using NASA's infrared Spitzer space telescope, the researchers observed that the planet absorbs part of the spectrum starlight in a way that can only be explained by the presence of water vapour in its atmosphere. 'We're thrilled to have identified clear signs of water on a planet that is trillions of miles away,' said Dr Giovanna Tinetti, a European Space Agency fellow at the Institute of Astrophysics of Paris in France, who led the study with an international team of researchers. 'Although HD 189733b is far from being habitable, and actually provides a rather hostile environment, our discovery shows that water might be more common out there than previously thought, and our method can be used in the future to study more 'life-friendly' environments,' Dr Tinetti added. Instead of a rocky world like Earth, HD 189733b is large, about 1.15 times the mass of Jupiter. Located just 4.5 million kilometres from its star, it orbits it in 2.2 days. In comparison, Earth is 150 million kilometres from the Sun; even Mercury, the innermost planet, is 70 million kilometres away. Astronomers classify such worlds as 'hot jupiters'. HD 189733b's atmospheric temperature is about 1000 Kelvin (a little more than 700°C) or higher, meaning that the significant amounts of water vapour in the atmosphere cannot condense to fall as rain or form clouds. The temperature would have to be about five times lower to form clouds of water vapour or rain. Although a gas giant, the planet is an unlikely candidate in the search for life. Nevertheless, these results increase hopes for the detection of water on other rocky planets, which astronomers hope to discover in the near future.