About this world
TOI-789 b is an Earth-sized planet orbiting TOI-789, a cool red dwarf (type M3V) 142 light-years from Earth. It is about 1.2 times the size of Earth and holds 3.7 Earth masses. It completes an orbit every 5.45 days at 0.043 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 448 K (175 °C): far too hot for liquid water on its surface. By the "cosmic shoreline", it has likely held on to an atmosphere.
It was discovered in 2026 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. TOI-789 has 3 known planets; the others are TOI-789 c and TOI-789 d.