TOI-237: A Small Red Dwarf with Two Earth-Like Planets

TOI-237 is an M4.5 V star, a small, cool red dwarf, located 124 light-years away. Its reported mass estimate is 0.179 solar masses, its reported radius estimate is 0.211 solar radii, and its reported temperature is 3210 K, all smaller or cooler than the Sun's corresponding values. The star's age is given as a reported lower limit of 4.5 billion years. Two planets orbit this host, both discovered by transit, the method in which a planet passing in front of its star from our viewpoint causes a small dip in observed brightness.

TOI-237 b was discovered in 2020 and has a reported orbital period of 5.44 days and a radius of 1.44 Earth radii. TOI-237 c was discovered in 2026 and has a reported orbital period of 1.74 days and a radius of 1.21 Earth radii. Both are classified as Earth-like, a size class that stays within 1.5 times Earth's radius, and each has a reported radius estimate larger than Earth's. Among the listed planets, TOI-237 c has the shortest year by reported estimates (1.74 days) and the smallest radius by reported estimates (1.21 Earth radii), while TOI-237 b has the longest year by reported estimates (5.44 days) and the largest radius by reported estimates (1.44 Earth radii).