KOI-256

Did You Know?

• The acronym KOI stands for Kepler object of interest, meaning the system was cataloged by the Kepler spacecraft during its search for extrasolar planets using the transit method.
• The number 256 is the object's catalog number.

Characteristics

Initial Kepler observations suggested a central red dwarf with a temperature of 3639 K and a candidate exoplanet with an orbital period of 1.38 days, a temperature of 1160 K, and a semi-major axis of 0.021 AU. Muirhead et al. (2012) refined the candidate parameters to a temperature of 726 K and a semi-major axis of 0.016 AU. Further observations with the Hale Telescope at Palomar Observatory using the radial velocity method showed the red dwarf wobbling too much for a planetary-mass object, indicating a white dwarf companion. Ultraviolet data from the GALEX spacecraft revealed significant red dwarf activity, supporting this. Re-analysis of Kepler data showed gravitational lensing when the white dwarf transited the red dwarf. The red dwarf has a temperature of 3450 K, while the white dwarf has a temperature of 7100 K, a mass much larger than its Earth-like size, and the red dwarf orbits the smaller but more massive white dwarf.