Introducing Earth's distant new neighbour
A planet the size of Jupiter has been discovered 1,500 light-years from Earth. Named Corot-9b after the telescope operated by the Centre National d'Études Spatiales (CNES) in France, the planet orbits a star located in the 'snake' constellation, Serpens Cauda. Details of the discovery are published in Nature. A European-led team of 60 international astronomers identified the planet after 145 days of observations during the summer of 2008 using COROT ('Convection, rotation and planetary transits'), a space telescope satellite constructed with support from four EU Member States, Brazil and the European Space Agency (ESA). Further observations at the European Southern Observatory (ESO) in Chile, using the HARPS (High Accuracy Radial Velocity Planet Searcher) instrument attached to a 3.6-metre telescope, allowed the astronomers to confirm that Corot-9b is actually an exoplanet (or 'extrasolar planet', a planet outside our solar system) with a mass similar to that of Jupiter. Dr Claire Moutou from Laboratoire d'Astrophysique de Marseille in France said Corot-9b is likely to become a Rosetta stone in this research field. 'This is a normal, temperate exoplanet just like dozens we already know, but this is the first whose properties we can study in depth,' she explained. Made up mostly of hydrogen and helium, Corot-9b may contain up to 20 Earth masses of heavier matter such as water and rock. The astronomers believe that Corot-9b is the first exoplanet that shows a resemblance to planets in our own solar system, particularly Jupiter and Saturn. 'Our analysis has provided more information on Corot-9b than for other exoplanets of the same type,' added Dr Didier Queloz from the University of Geneva in Switzerland. 'It may open up a new field of research to understand the atmospheres of moderate- and low-temperature planets, and in particular a completely new window in our understanding of low-temperature chemistry.' The newly discovered exoplanet is the first transiting planet with an orbit that is almost circular and takes a longer period to complete. Corot-9b transits its star every 95 days, a little longer than Mercury takes to orbit the Sun. A transit takes place when a celestial body passes in front of its host star, causing a type of eclipse. This results in a diminishment of the star's light and allows experts to calculate a planet's mass, diameter, density and temperature. In fact, this 'transit' method has been used to discover 70 exoplanets in recent history. Experts have estimated that since Corot-9b orbits a star cooler than our Sun, its temperature could lie between -23°C and 157°C. 'Only 25 years ago no extrasolar planets were known, and today we know of more than 400,' said Dr Avi Shporer from the University of California, Santa Barbara in the US. 'Undoubtedly, many more exciting discoveries await in the future.'
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