Kepler-444 and Its Five Sub-Earth Planets

Kepler-444 is a K-type star located 119 light-years away, with five planets known to orbit it. The star's reported mass estimate is 0.758 solar masses, its radius estimate is 0.752 solar radii, and its temperature is 5050 K. Its age is given as 11.2 billion years. The star's mass and radius estimates are both smaller than the Sun's, and its temperature is cooler than the Sun's.

All five planets were discovered by transit in 2015 and are classified as Sub-Earths, meaning their radii are smaller than Earth's. Kepler-444 b has an orbital period of 3.6 days and a radius of 0.403 Earth radii. Among the listed planets, it has the shortest year and the smallest radius. Kepler-444 c orbits in 4.55 days with a radius of 0.497 Earth radii, giving it the second-shortest year and second-smallest radius among the listed planets. Kepler-444 d has an orbital period of 6.19 days and a radius of 0.53 Earth radii. Kepler-444 e orbits in 7.74 days with a radius of 0.546 Earth radii, the second-longest year and second-largest radius among the listed planets. Kepler-444 f completes an orbit in 9.74 days with a radius of 0.741 Earth radii. Among the listed planets, it has the longest year and the largest radius. Every one of the five planets has a reported radius estimate smaller than Earth's.