Kepler-210: A Cool Red Dwarf with Two Neptune-Like Planets

Kepler-210 is a red dwarf of spectral type M0 V, a small, cool star with a reported mass of 0.77 solar masses and a radius of 0.7 solar radii. Its reported temperature is 4590 K, and its age is 1.78 billion years. This star lies 759 light-years away and hosts two known planets, both discovered in 2014 by the transit method, in which a planet passes in front of its star from our viewpoint and causes a small dip in observed brightness.

The two planets are Kepler-210 b and Kepler-210 c, both classified as Neptune-like. Kepler-210 b has an orbital period of 2.45 days and a radius of 2.94 Earth radii. Kepler-210 c has an orbital period of 7.97 days and a radius of 3.62 Earth radii. Among the listed planets, Kepler-210 b has the shortest year and the smallest radius, while Kepler-210 c has the longest year and the largest radius.

The star's reported mass, radius, and temperature are all smaller or cooler than the Sun's. Both planets have reported radius estimates larger than Earth's.