COROT-7b

COROT-7b is an exoplanet that orbits the star "COROT-7" in the constellation Monoceros, 489 light years from Earth. 
It was first detected by the French-led COROT mission and reported in 2009. Until the announcement of Kepler-10b in January 2011, it was the smallest exoplanet to have its diameter measured, at 1.58 times that of the Earth which would give it a volume 3.95 times Earth's. It was the first potential extrasolar terrestrial planet to be found. The planet is also notable for its very short orbital period: it revolves around its host star in about 20 hours.