CoRoT is a satellite devoted to the study of the internal structure of stars and to the hunt for planets outside the Solar System (exoplanets). It was launched on 27 december 2006, and the initial planned duration of the mission was 3 years.
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| An illustration showing the French astronomical satellite CoRoT. © CNES/DUCROS David, 2006 |
CoRoT measured vibrations of various types of stars, some similar to the Sun, some more massive or older. The CNES satellite also revealed that most stars are much more variable than thought. On the exoplanets side, as of end November 2011, CoRoT had detected 625 candidate exoplanets, 25 of which have been confirmed by ground telescopes. And that’s not all, since CoRoT has also discovered what is thought to be the first Earth-like planet outside the solar system: CoRoT-7b, confirmed in 2009.
Indeed, CoRoT has collected a diverse haul of exoplanets with diameters varying by as much as a factor of 10 and densities as much as a factor of 200.
Regarding density, CoRoT-3b is a special case. Its mass is 21.66 times the mass of the planet Jupiter. When it was originally discovered, it was believed to have a radius significantly smaller than that of Jupiter. This would have implied it had properties intermediate between those of planets and brown dwarfs. Later more detailed analysis revealed that the object's radius is similar to that of Jupiter, which fits with the expected properties of a brown dwarf with the mass of CoRoT-3b. The mean density of CoRoT-3b is 26,400 kg/m3, greater than that of osmium under standard conditions. This high density is reached because of the extreme compression of matter in the object's interior: in fact, the radius of CoRoT-3b is in agreement with predictions for an object composed mainly of hydrogen. The surface gravity is correspondingly high, over 50 times the gravity felt at the surface of the Earth.
CoRoT, which name means “Convection, Rotation & planetary Transits” has two scientific goals: the search for planets orbiting around other stars than our Sun, and in particular for planets similar to our Earth; and the detection of the vibrations of the stars in order to sound their internal structure (stellar seismology). This satellite, with its 27 cm telescope, is orbiting 896 km above Earth. It was designed to detect tiny light variations from stars distant of up to a few hundreds light years from the Sun during long observation sessions.
Sources:
- The CoRoT satellite: 3 more years to hunt for planets and to listen to the music of stars, CNES, October 26, 2009
- CoRoT at a glance, CNES
- CoRoT’s haul of 25 exoplanets, CNES, December 23, 2011
