About this world
K2-233 d is a sub-Neptune orbiting K2-233, an orange dwarf (type K3) 220 light-years from Earth. It is about 2.4 times the size of Earth and holds 10 Earth masses. It completes an orbit every 24.4 days at 0.15 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 525 K (252 °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 2018 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction. K2-233 has 3 known planets; the others are K2-233 b and K2-233 c.