Kepler-1388 and Its Four Planets

Kepler-1388 is a star located 1480 light-years away, and four planets have been identified orbiting it. The host star is estimated to be 4.47 billion years old, with a mass of 0.63 solar masses and a radius of 0.61 solar radii. Its reported temperature is 4100 K. The star's 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 discovered by transit in 2016. 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-1388 b is a Neptune-like planet with an orbital period of 12.3 days and a radius of 2.59 Earth radii. Among the listed planets, it has the second-shortest year and the second-largest radius. Kepler-1388 c is a Super-Earth with an orbital period of 5.54 days and a radius of 2.26 Earth radii. Among the listed planets, it has the shortest year and the smallest radius.

Kepler-1388 d is a Neptune-like planet with an orbital period of 21 days and a radius of 2.86 Earth radii. Among the listed planets, it has the second-longest year and the largest radius. Kepler-1388 e is a Super-Earth with an orbital period of 37.6 days and a radius of 2.46 Earth radii. Among the listed planets, it has the longest year and the second-smallest radius. The reported radius estimate of each of these four planets is larger than Earth's.