GJ 357 d exoplanet. Illustration of the exoplanet GJ 357 d, which orbits an M-type dwarf star located 31 light-years away in the constellation Hydra. GJ 357 d is at least 6.1 times Earth's mass, and orbits the star every 55.7 days. GJ 357 d is located within the outer edge of its star's habitable zone, where it receives about the same amount of stellar energy from the host star as Mars does from the Sun. Without an atmosphere, it has a temperature of -53 degrees Celsius, predictions would suggest the planet is more glacial than habitable. GJ 357 d was discovered by measuring changes in the host star's speed of motion (radial velocity). Radial velocity changes indicate the gravitational pull of other nearby objects and is a method of discovering exoplanets.