About this world
K2-389 b is a sub-Neptune orbiting K2-389, a yellow, Sun-like star (type G3) 845 light-years from Earth. It is about 2.3 times the size of Earth. It completes an orbit every 8.58 days at 0.082 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 932 K (659 °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 2022 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction. K2-389 has 2 known planets; the others are K2-389 c.