About this world
TOI-5789 c is a sub-Neptune orbiting TOI-5789, an orange dwarf (type K1V) 66.7 light-years from Earth. It is about 2.9 times the size of Earth and holds 5 Earth masses. It completes an orbit every 12.9 days at 0.1 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 718 K (445 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
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-5789 has 4 known planets; the others are TOI-5789 b, TOI-5789 d and TOI-5789 e.