The Kepler-26 System: A Cool Red Dwarf and Four Worlds

Kepler-26 is a small, cool red dwarf of spectral type M0 V, located 1090 light-years away. Its reported mass estimate is 0.62 solar masses, its radius 0.6 solar radii, and its temperature 4100 K, all smaller or cooler than the Sun's corresponding values. The star is roughly 2.95 billion years old. Four planets are known to orbit this host, and all four were found 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.

Kepler-26 b and Kepler-26 c were both discovered in 2011 and both are Neptune-like. Kepler-26 b has a radius of 2.78 Earth radii and a mass of 5.12 Earth masses; its mean density is 1.31 g/cm³, 0.238 times Earth's. Kepler-26 c has a radius of 2.72 Earth radii and a mass of 6.2 Earth masses, with a mean density of 1.7 g/cm³, 0.308 times Earth's. Both have radii and masses larger than Earth's, and their orbital periods are 12.3 days and 17.3 days respectively.

Kepler-26 d and Kepler-26 e were both discovered in 2014. Kepler-26 d is Earth-like, with a radius of 1.07 Earth radii and an orbital period of 3.54 days, the shortest year among the listed planets. Kepler-26 e is a Super-Earth with a radius of 2.41 Earth radii and an orbital period of 46.8 days, the longest year among the listed planets. Kepler-26 d also has the smallest radius among the listed planets, while Kepler-26 b has the largest.