About this world
TOI-178 b is an Earth-sized planet orbiting TOI-178, an orange dwarf (type K) 204 light-years from Earth. It is about 1.2 times the size of Earth and holds 0.96 Earth masses. It completes an orbit every 1.91 days at 0.026 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,040 K (767 °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 in one spectroscopic observation by the James Webb Space Telescope.
It was discovered in 2021 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. TOI-178 has 6 known planets; the others are TOI-178 c, TOI-178 d, TOI-178 e, TOI-178 f and TOI-178 g.