Exoplanet 432

CoRot-9b is the name of the 71st extrasolar planet discovered using the transit method of measuring the light blocked as the planet moves between the star and the detector.

In the paper announcing the discovery, the team describe it as having a 95 day orbit around the star CoRot-9 at a distance 0.36 times that of the Sun-Earth distance. The orbit is eccentric (elliptical) with eccentricity of about 0.11. The importance of this is that most of the planets discovered by transits are ‘Hot Jupiters’, extremely close in to their stars under the influence of gravitational tidal forces and strong blasts of particle and photon radiation. This one is the furthest out Jupiter like planet with an estimated photospheric temperature of 250-430K, relatively frigid compared to the previous ones, making it more of a Warm Jupiter. The distance also ensure gravitational pulling at the atmosphere is limited and the inferences they have about the composition of the planet suggest something close to Jupiter or Saturn. In effect, this is the first time the planetary evolution models based on our own solar system have found a planet close enough to those we know to describe it pretty well with little alteration for its environment.

The COnvection ROtation and planetary Transit space telescope, or CoRoT, which discovered the object is in a polar circular orbit 896 km in altitude. It spends its time doing stellar seismology and searching for the small variations induced by extrasolar planetary transits. It is equipped with a 27cm afocal telescope and four CCDs to do its work.

CoRoT-9, the star about which the planet orbits, is a 13.7th magnitude star located at a distance of 490 parsecs (1,500 light years) in the constellation of Srepens the Snake. It is a G3V type star with a mass close to our sun, a radius slightly smaller, metalicity very similar and an effective temperature of 5625 K. The planet is 0.84 Jovian masses with a slightly larger radius of 1.05 Jovian radii, according to its entry in the Extrasolar Planet Encyclopedia.

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