Kepler-51 and Its Four Planets

Kepler-51 is a star 2560 light-years away with four planets orbiting it. The host star is 0.5 billion years old, has a mass of 0.985 solar masses, a radius of 0.881 solar radii, and a temperature of 5670 K. Its 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.

All four planets were detected by transit, the dimming of a star when a planet crosses in front of it. Kepler-51 b and c were discovered in 2012, d in 2014, and e in 2024 by transit timing variations.

Kepler-51 b is Jupiter-like, with a mass of 2.1 Earth masses, a radius of 7.1 Earth radii, and an orbital period of 45.2 days. Among the listed planets, it has the shortest year and the smallest reported mass.

Kepler-51 c is also Jupiter-like, with a mass of 4 Earth masses, a radius of 9 Earth radii, and an orbital period of 85.3 days. Among the listed planets, it has the second-shortest year and the second-smallest reported mass.

Kepler-51 d is Jupiter-like, with a mass of 7.6 Earth masses, a radius of 9.7 Earth radii, and an orbital period of 130 days. Among the listed planets, it has the largest reported mass and the second-longest year.

Kepler-51 e has a mass of 5.4 Earth masses and an orbital period of 264 days. Among the listed planets, it has the longest year and the second-largest reported mass.