Extrasolar Planet Kepler-10 b

The exoplanet Kepler-10 b is known for being the first rocky planet confirmed in the sample of exoplanet canidates observed by the Kepler mission. (The announcement paper is Batalha et al. 2011.)

The star Kepler-10 is about 564 light years from Earth, its mass is similar to our Sun ($M=0.895\pm0.06 \ M_{\odot}$), and its size is also similar to our Sun ($R=1.056\pm0.021 \ R_{\odot}$). The planet itself has a lower limit on its mass of about 4.5 Earth masses, and a radius of about 1.39 Earth radii. The planet's average denisty is thus 1.68 times that of Earth. Its surface gravity is about 2.4 times that of Earth.

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The maximum star-planet distance (semimajor axis) is tiny, only just 1.7% of the Earth-Sun distance (0.017 astronomical units (AU)). The orbital period is correspondingly short, as 0.837 Earth days. This extremely close-in orbit is not common for a planet that is supposed to terrestrial.

You can see from the radius versus mass diagram for confirmed exoplanets that the regime of small mass and radius (terrestrial planet candidates) is still only sparsley populated.

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File under: Kepler-10b; Rocky terrestrial planet in the Kepler candidates sample.