Kepler-28b is an extrasolar planet orbiting the star Kepler-28. It is a transiting planet that is smaller than Jupiter that orbits very closely to Kepler-28.
Discovery | |
---|---|
Discovered by | Jason Steffen et al. |
Discovery site | Kepler Space Observatory |
Discovery date | 25 January 2012 |
Detection method | Transit |
Orbital characteristics | |
Semi-major axis | 0.05375 AU (8,041,000 km)[1] |
Orbital period (sidereal) | 5.91227[1] d |
Star | Kepler-28 |
Physical characteristics | |
Mean radius | 2.41+0.04 −0.17[1] REarth |
Mass | 8.8+3.8 −3.1MEarth[2] |
Temperature | 743 K[2] |
Kepler-28 is the host star of Kepler-28b, and is alternatively known as KOI-870 and KIC 6949607. The star is smaller, less massive, and cooler than the Sun, with (respectively) a radius 0.7 times of the Sun; a mass 0.75 times of the Sun; and an effective temperature of 4590 K.[3] The star has a high metallicity with relation to the Sun, as it has a metallicity of [M/H] = 0.34. With an apparent magnitude of 15.05, Kepler-28 is effectively invisible to the naked eye from Earth.[4]
Kepler-28b is a gas giant. Upon discovery, it was poorly characterized, with only upper mass limit of 1.51 times the mass of Jupiter can be ascertained from dynamical simulations. The planet, which transits its host star, completely passes across the face of Kepler-28 in 2.77 hours.[4] The ratio of its orbital period with that of Kepler-28c is 1.52.[5] In 2016, improved radial velocity data has allowed to classify Kepler-28b as a small (sub-Neptune) gas giant.[2]