About this world
GJ 357 b is an Earth-sized planet orbiting GJ 357, a cool red dwarf (type M2.5V) 30.8 light-years from Earth. It is about 1.2 times the size of Earth and holds 1.8 Earth masses. It completes an orbit every 3.93 days at 0.036 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 518 K (245 °C): far too hot for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock. Its atmosphere has already been studied: 4 spectroscopic observations, all of them with the James Webb Space Telescope.
It was discovered in 2019 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. GJ 357 has 3 known planets; the others are GJ 357 c and GJ 357 d.