GJ 357 c exoplanet. Illustration of the exoplanet GJ 357 c, which orbits an M-type dwarf star located 31 light-years away in the constellation Hydra. GJ 357 c has a mass at least 3.4 times Earth's and orbits the star every 9.1 days with a temperature around 127 degrees Celsius. GJ 357 c's orbit is slightly tilted relative to other planets in the system and 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.