Kepler-332: A Cool Star with Three Small Planets

Kepler-332 is a star located 1,120 light-years away. It is 2.82 billion years old and has a mass of 0.8 solar masses, a radius of 0.74 solar radii, and a temperature of 5010 K. Its mass and radius are smaller than the Sun's, and its temperature is cooler. Three planets orbit this host: Kepler-332 b, Kepler-332 c, and Kepler-332 d. All three were discovered in 2014 by the transit method, in which a planet passes in front of its star from our viewpoint, causing a small dip in observed brightness. Repeated dips help establish orbital periods.

All three planets are classified as Earth-like, a size class that stays within 1.5 times Earth's radius. Each has a reported radius larger than Earth's. Kepler-332 b has a radius of 1.17 Earth radii and an orbital period of 7.63 days, the shortest year among the listed planets. Kepler-332 c has a radius of 1.09 Earth radii and an orbital period of 16 days, the second-shortest year among the listed planets and the smallest radius among them. Kepler-332 d has a radius of 1.18 Earth radii and an orbital period of 34.2 days, the longest year and the largest radius among the listed planets.