Kepler-357: A Distant Star With Three Known Worlds

Kepler-357 is a star located 2250 light-years away, and three planets have been found in orbit around it. The star is estimated to be 4.47 billion years old, with a reported mass estimate of 0.81 solar masses and a reported radius estimate of 0.77 solar radii. Its reported temperature is 5030 K. Compared with the Sun, the star's reported mass and radius estimates are smaller, and its reported temperature is cooler.

All three 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-357 b is a Super-Earth with an orbital period of 6.48 days and a radius of 1.84 Earth radii. Among the listed planets, it has the shortest year and the smallest radius by reported estimates.

Kepler-357 c is a Neptune-like planet with an orbital period of 16.9 days and a radius of 2.67 Earth radii. Its reported radius estimate is larger than Earth's, and among the listed planets it has the second-shortest year and the second-smallest radius by reported estimates.

Kepler-357 d is also Neptune-like, with an orbital period of 49.5 days and a radius of 3.43 Earth radii. Its reported radius estimate is larger than Earth's, and among the listed planets it has the longest year and the largest radius by reported estimates.

Planet size classes compare radius with Earth's: a Super-Earth reaches 2.5 times Earth's radius, while a Neptune-like planet reaches 4 times. Earth radii compare radius, not volume, and solar masses and radii compare stellar mass and radius with the Sun.