Kepler-247: A Cool Star and Its Four Worlds

Kepler-247 is a K-type star located 2160 light-years away. It is cooler than the Sun at 5130 K, with a reported mass of 0.84 solar masses and a radius of 0.8 solar radii, making it both less massive and smaller than the Sun. The star is 4.27 billion years old. Four planets are known to orbit Kepler-247.

Kepler-247 b is a Super-Earth with a radius of 1.64 Earth radii and an orbital period of 3.34 days. Kepler-247 c is Jupiter-like, with a radius of 4.09 Earth radii and a period of 9.44 days. Both were found by transit. Kepler-247 d, also Jupiter-like, has a radius of 4.5 Earth radii, a mass of 50 Earth masses, and an orbital period of 20.5 days. Its mean density is 3.02 g/cm³, 0.549 times Earth's. This planet was also discovered by transit.

KOI-884 e is distinct: it was discovered in 2014 via Transit Timing Variations, indicating its presence was inferred through gravitational effects on another planet's transit schedule. It has a mass of 66.1 Earth masses and an orbital period of 31.1 days. The mass of KOI-884 e exceeds Earth's, as do the masses of Kepler-247 d. Among the listed planets, KOI-884 e has the longest year at 31.1 days, while Kepler-247 b has the shortest at 3.34 days. Kepler-247 d has the second-longest year, and Kepler-247 c has the second-shortest.

The star's reported temperature is cooler than the Sun's, and its reported mass and radius are smaller than the Sun's. Kepler-247 b, c, and d all have radii larger than Earth's.