Radial velocity observations measuring the gravitational tug
exerted by KOI-254 b on KOI-254 gives KOI-254 b a mass of 0.505 times the mass
of Jupiter. The estimated equilibrium temperature of KOI-254 b is 1000 degrees
Kelvin. What makes KOI-254 b unique is that it is the first known Jupiter-mass
planet in a short period orbit around a red dwarf star. Apart from KOI-254 b,
there is no known planet above 0.2 times the mass of Jupiter orbiting a red
dwarf star with an orbital period of less than 10 days. Given the fact that
close-in Jupiter mass planets should be readily detected around red dwarf
stars, the lack of such planets mean that KOI-254 b is likely to be the only
known example of a hot Jupiter around a red dwarf star for some time.
Thursday, May 31, 2012
An Odd Planet
A recent paper by John Asher Johnson et al. (2012) titled “Characterizing
the Cool KOIs. II. The M Dwarf KOI-254 and Its Hot Jupiter” describes the
discovery of the first hot Jupiter around a red dwarf star. Red dwarf stars are
the coolest and least massive type of stars, and they also make up the majority
of stars. The star involved is called KOI-254 and a gas giant planet orbits it
once every 2.455 days. This gas giant planet is designated KOI-254 b and it was
originally discovered by the Kepler mission from its periodic transits in front
of KOI-254. During each transit, KOI-254 dims by 3.909 percent and from this,
the size of KOI-254 b is estimated to be 0.96 times the diameter of Jupiter.