GJ 15 A: A Nearby Red Dwarf with Two Known Planets

GJ 15 A is an M2 V star, a small, cool red dwarf, located 11.6 light-years away. Its spectral class places it among the cooler, redder stars. The star has a reported mass of 0.375 solar masses, a radius of 0.386 solar radii, and a temperature of 3570 K. Each of these estimates is smaller or cooler than the corresponding value for the Sun. Two planets are known to orbit this host.

GJ 15 A b was discovered in 2014 by the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion. It has a minimum mass of 3.03 Earth masses and an orbital period of 11.4 days. That minimum mass is larger than Earth's, and among the listed planets it is the smallest minimum mass. Its year is also the shortest among the listed planets.

GJ 15 A c was discovered in 2018, also by radial velocity. It has a minimum mass of 36 Earth masses and an orbital period of 7600 days. Its minimum mass is larger than Earth's and is the largest among the listed planets, and its year is the longest among them. A minimum mass is a lower bound on a planet's true mass, so these figures represent the least mass each planet could have.