GJ 357 b exoplanet. Illustration of the exoplanet GJ 357 b, which orbits an M-type dwarf star located 31 light-years away in the constellation Hydra. NASA's Transiting Exoplanet Survey Satellite (TESS) satellite detected the exoplanet passing in front the star which causes a dimming of the star's light. GJ 357 b is about 22% larger than Earth and orbits 11 times closer to its star than Mercury does the Sun. GJ 357 b is described as a 'Hot Earth' with a possible atmospheric temperature of around 254 degrees Celsius.