2M1207b

2M1207b is a planetary-mass object orbiting the brown dwarf 2M1207, in the constellation Centaurus, approximately 170 light-years from Earth.

[6] It is believed to be from 5 to 6 times the mass of Jupiter[3] and may orbit 2M1207 at a distance roughly as far from the brown dwarf as Pluto is from the Sun.

[7] The object is a very hot gas giant; the estimated surface temperature is roughly 1200 K (930 °C or 1700 °F),[3] mostly due to gravitational contraction.

[5] In December 2005, American astronomer Eric Mamajek reported a more accurate distance (53±6 parsecs) to 2M1207b using the moving-cluster method.

[8] As an unlikely possibility, Mamajek and Michael Meyer have suggested that the planet is actually much smaller, but is radiating away heat generated by a recent collision.

[16][17] The mass ratio of 2M1207b and 2M1207 is approximately 0.22, which exceeds the L4/L5 instability threshold and therefore means 2M1207b does not qualify as an exoplanet under the IAU's definition.

[19] On the other hand, the discovery of marginal cases like Cha 110913-773444—a free-floating, planetary-mass object—raises the question of whether distinction by formation is a reliable dividing line between stars/brown dwarfs and planets.

Infrared image of 2M1207 (blueish) and 2M1207b (reddish). The two objects are separated by less than one arc second in Earth's sky. Image taken using the ESO 's 8.2m Yepun VLT .