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An international team has discovered water on an extra-solar planet for only the second time. The researchers, led by Giovanna Tinetti of the European Space Agency and 51¹ú²úÊÓƵ College London's department of physics and astronomy, found that as the planet, known as HD189733b, passes in front of its Sun, it absorbs light in a way that can only be explained by the presence of water vapour in its atmosphere. The discovery was made using Nasa's Spitzer earth-orbiting telescope and is reported in the journal Nature .