Kepler-28: A Cool Dwarf with Two Super-Earths

Kepler-28 is an M0 V star, a small, cool red dwarf, located 1430 light-years away. Its reported mass estimate is 0.77 solar masses and its reported radius estimate is 0.71 solar radii, both smaller than the Sun's. The star's reported temperature is 4690 K, cooler than the Sun's, and its age is 2.24 billion years. Two planets orbit this host.

Kepler-28 b and Kepler-28 c are both classified as Super-Earths, discovered by transit in 2011. Kepler-28 b has a mass of 1.63 Earth masses, a radius of 1.96 Earth radii, and an orbital period of 5.91 days. Kepler-28 c has a mass of 2.06 Earth masses, a radius of 1.86 Earth radii, and an orbital period of 8.99 days. Both planets' reported radius and mass estimates are larger than Earth's, and among the listed planets Kepler-28 b has the shortest year by reported estimates while Kepler-28 c has the longest. Kepler-28 b also has the largest radius and the smallest reported mass, while Kepler-28 c has the smallest radius and the largest reported mass. Kepler-28 b's mean density is 1.19 g/cm³, 0.217 times Earth's; Kepler-28 c's is 1.77 g/cm³, 0.322 times Earth's.