Corot-20b is an extrasolar planet discovered in 2009 by the French COROT satellite. It is located about 1,500 light-years away from Earth in the constellation of Monoceros, and has a mass approximately half that of Jupiter. Its discovery was announced on February 3, 2009.
This planet was detected using the transit method; it transits (or crosses in front of) its host star once every 20 days. The depth of the transit (the amount by which the star’s brightness decreases when the planet passes in front of it) indicates that the planet has a diameter slightly larger than that of Saturn. The small size and short orbital period imply that Corot-20b is a hot Jupiter, a type of gas giant planet with a very close orbit to its host star.
The host star, Corot-20, is slightly smaller and cooler than the Sun; it has about 80% of the Sun’s mass and radius, and only 60% of its luminosity. Based on its spectral type (G8V), Corot-20 appears to be somewhat younger than our Sun at around 4 billion years old. However, further study will be needed to confirm this estimate.