spacetoday.net: Spacecraft discovers smallest exoplanet

Posted: Fri, Feb 6, 2009, 5:34 AM ET (1034 GMT)
COROT-Exo-7b illustration (ESA)

Scientists using a European spacecraft claim to have discovered the smallest extrasolar planet to date, a world that orbits so close to its parent star its surface could be made of molten rock. Astronomers discovered the planet, COROT-Exo-7b, with the French astronomy spacecraft COROT by detecting when the planet transited across the disc of the star some 390 light-years away. The planet has a diameter about twice that of the Earth, making the planet the smallest known exoplanet in terms of diameter; it may not be the least massive exoplanet, though, with a mass currently estimated at between 5 and 11 times that of the Earth. The planet orbits so close to its star that it completes one orbit in 20 hours, implying a surface temperature of 1,000-1,500 degrees Celsius. At those temperatures, the planet could have a surface of molten rock, or be a mix of rock and water vapor.