CoRoT-7b

CoRoT-7b (previously named CoRoT-Exo-7b) is an exoplanet orbiting the star CoRoT-7 in the constellation of Monoceros, from Earth. It was first detected photometrically by the French-led CoRoT mission and reported in February 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) and the first potential extrasolar terrestrial planet to be found. The exoplanet has a very short orbital period, revolving around its host star in about 20 hours. Combination of the planet's diameter derived from transit data with the planet's mass derived from radial velocity measurements means that the density of CoRoT-7b is about the same as that of Earth; therefore, CoRoT-7b is a terrestrial planet like Earth and not a gas giant like Jupiter. The radial velocity observations of CoRoT-7 also detected a second super-Earth, CoRoT-7c, which has a mass 8.4 times that of Earth and orbits every 3.7 days at a distance of . CoRoT-7b was found by observing its parent star's periodic decrease in apparent magnitude caused by the planet's transit in front of the star as seen from Earth. Measuring this dip in brightness, together with a size estimate for the star, allows calculating the planet's size. (See Transit method.) The space mission CoRoT observed the star CoRoT-7, in the stellar field LRa01, from October 15, 2007, to March 3, 2008. During this period, 153 periodic transit signals of 1.3 h duration with a depth of 3.4 × 10−4 were registered. After 40 days of data acquisition, the Alarm mode pipeline algorithm detected the shallow signal of CoRoT-7b, starting the follow-up observations from the ground to get a confirmation of the planetary nature of the transiting object. The discovery of CoRoT-7b was announced a year later on February 3, 2009, during the CoRoT Symposium 2009 in Paris. It was published in a special issue of the journal Astronomy and Astrophysics dedicated to results from CoRoT.