About this world
K2-266 d is a sub-Neptune orbiting K2-266, an orange dwarf 253 light-years from Earth. It is about 2.9 times the size of Earth and holds 8.9 Earth masses. It completes an orbit every 14.7 days at 0.1 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 538 K (265 °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. K2-266 has 4 known planets; the others are K2-266 b, K2-266 c and K2-266 e.