Kepler-446: A Cool Red Dwarf and Its Three Small Worlds

Kepler-446 is an M4 host star located 314 light-years away. Its mass is 0.4 solar masses, its radius is 0.38 solar radii, and its temperature is 3450 K, making it cooler than the Sun. The star is 3.72 billion years old. Three planets orbit this host: Kepler-446 b, Kepler-446 c, and Kepler-446 d.

All three planets were discovered by transit in 2015. Kepler-446 b is a Super-Earth with a radius of 1.5 Earth radii and an orbital period of 1.57 days. Kepler-446 c is Earth-like, with a radius of 1.11 Earth radii and an orbital period of 3.04 days. Kepler-446 d is also Earth-like, with a radius of 1.35 Earth radii and an orbital period of 5.15 days.

Among the listed planets, Kepler-446 b has the shortest year by reported estimates at 1.57 days, while Kepler-446 d has the longest at 5.15 days. Kepler-446 c falls in between with the second-shortest year at 3.04 days. In terms of radius, Kepler-446 c has the smallest radius among the listed planets at 1.11 Earth radii, and Kepler-446 b has the largest at 1.5 Earth radii. Kepler-446 d has the second-smallest radius at 1.35 Earth radii. The reported radius estimates for Kepler-446 b and Kepler-446 d are both larger than Earth's.

The host star's reported mass estimate is smaller than the Sun's, its reported radius estimate is smaller than the Sun's, and its reported temperature is cooler than the Sun's.