GJ 273 and Its Two Known Planets

GJ 273 is an M-type dwarf, a small, cool red star, lying 19.3 light-years away. Its spectral type is M3.5. The star has a reported mass of 0.29 solar masses, a radius of 0.293 solar radii, and a temperature of 3380 K, so both its mass and radius are smaller than the Sun's and its temperature is cooler. Two planets are known to orbit this host.

Both planets were found by the radial velocity method, which tracks the wobble a planet's gravity induces in its star, and both were announced in 2017. GJ 273 b has a minimum mass of 2.89 Earth masses and an orbital period of 18.6 days, while GJ 273 c has a minimum mass of 1.18 Earth masses and an orbital period of 4.72 days. Each minimum mass is a lower bound on the planet's true mass, and each is larger than Earth's. Among the listed planets, GJ 273 c has the shortest year, at 4.72 days, and the smallest minimum mass, at 1.18 Earth masses; GJ 273 b has the longest year, at 18.6 days, and the largest minimum mass, at 2.89 Earth masses.