Kepler-233: A Cool Star With Two Known Planets

Kepler-233 is a star located 2790 light-years away, with two planets reported to orbit it. The star is estimated to be 4.68 billion years old, with a mass of 0.84 solar masses, a radius of 0.8 solar radii, and a temperature of 5260 K. Its reported mass and radius estimates are smaller than the Sun's, and its reported temperature is cooler than the Sun's.

Both planets were discovered by transit in 2014. A transit occurs when a planet passes in front of its star from our viewpoint, causing a small dip in observed brightness; repeated dips help establish orbital periods. Kepler-233 b is a Super-Earth with an orbital period of 8.47 days and a radius of 2.43 Earth radii, larger than Earth's. Kepler-233 c is Neptune-like, with an orbital period of 60.4 days and a radius of 2.71 Earth radii, also larger than Earth's. Among the listed planets, Kepler-233 b has the shortest orbital period and the smallest radius by reported estimates, while Kepler-233 c has the longest orbital period and the largest radius by reported estimates.