Decent Look: UK astronomers find water on extra-solar planet

UK astronomers find water on extra-solar planet

Posted by nazim Friday, July 17, 2009

The researchers, led by Dr Giovanna Tinetti, an ESA fellow from the Institute d'Astrophysique de Paris and UCL (from 1st July), found that HD 189733b absorbs the starlight of its "sun", as it passes in front, in a way that can only be explained if it has water vapour in its atmosphere. This is the first time that astronomers have demonstrated for certain that water is present in an extra-solar planet with the infrared analysis of the planet's transit across its parent star providing the breakthrough.
Dr Tinetti, who is taking up a prestigious STFC Aurora Fellowship at UCL to study atmospheric signatures and biosignatures on planets beyond our solar system, said; "Although HD 189733b is far from being habitable, and is actually quite a hostile environment, our discovery shows how water might be common out there and how our method can be used in the future to study more life-friendly environments."
Dr Tinetti adds, "The 'holy grail' for today's planet hunters is to find an Earth-like planet that also has water in its atmosphere. That discovery, when it happens, will provide real evidence that planets outside of our Solar System might harbour life. So the discovery that water exists on an extra—solar gas giant is a vital milestone along that road of discovery."
This exciting discovery was made using NASA's Spitzer Earth-orbiting telescope, taking measurements at a number of key wavelengths in the infrared region of the spectrum that pick out the crucial signature of water. The water detection relied not only on Dr Tinetti's painstaking analysis, but also on the calculation of highly accurate water absorption parameters by Dr Bob Barber and Professor Jonathan Tennyson, also from UCL.
Dr Barber said, "Initial data included over 500 million individual absorption features and from this we calculated the absorption parameters. Each feature is unique, like a fingerprint, and provides vital clues about the amount of water present and the temperature of the atmosphere."
Professor Tennyson, who heads UCL's Physics and Astronomy Department, explained: "Parts of the atmosphere of HD 189733b are very hot – around 2000 degrees. You need the millions of lines we calculated to simulate this, putting in absorption accurately where it should be and – just as accurately – giving gaps for the light to get through the atmosphere, where it can."