COROT-Exo-7 b is not confirmed to be the smallest in mass discovered. COROT-Exo-7b has a diameter that is between 1.75 and 2 times that of the Earth, and orbits its star once every 20 hours. Its mass is less than 11 Earth masses.
The planet is about 455 light-years away in the constellation Monoceros.
COROT has found the smallest terrestrial planet ever detected outside the Solar System. The amazing planet is less than twice the size of Earth and orbits a Sun-like star. Its temperature is so high that it is possibly covered in lava or water vapour. About 330 exoplanets have been discovered so far, most of which are gas giants with characteristics similar to Jupiter and Neptune. The new find, COROT-Exo-7b, is different: its diameter is less than twice that of Earth and it orbits its star once every 20 hours. It is located very close to its parent star, and has a high temperature, between 1000 and 1500°C. Astronomers detected the new planet as it transited its parent star, dimming the light from the star as it passed in front of it. The density of the planet is still under investigation: it may be rocky like Earth and covered in liquid lava. It may also belong to a class of planets that are thought to be made up of water and rock in almost equal amounts. Given the high temperatures measured, the planet would be a very hot and humid place.
Tiniest exoplanet found A European satellite has spied the smallest and fastest-orbiting extrasolar planet to date, bringing astronomers closer to finding a habitable planet outside our Solar System. The Convection, Rotation and Planetary Transits (CoRoT) mission, a European Space Agency satellite that scans for exoplanets - planets outside our Solar System - has spied a rocky planet whose radius is slightly less than twice that of Earth. At 5 - 10 Earth masses, the planet is not the lowest-mass extrasolar planet ever found, but the mass and radius measurements suggest a density similar to that of earth.