Gliese 12 and Its Sub-Earth Planet

Gliese 12 is an M4 V star 39.8 light-years away. The spectral type describes a small, cool red dwarf, and the star's reported temperature of 3250 K is cooler than the Sun's. Its reported mass of 0.241 solar masses and radius of 0.269 solar radii are each smaller than the Sun's. The star's age is 7 billion years.

One planet orbits this host. Gliese 12 b was discovered in 2024 by the transit method, in which a planet passing in front of its star briefly dims the observed light. The planet is classified as a Sub-Earth, meaning its radius is smaller than Earth's. Its radius of 0.93 Earth radii is indeed smaller than Earth's. The planet has a mass of 0.95 Earth masses, an orbital period of 12.8 days, and a mean density of 6.51 g/cm³, 1.18 times Earth's.