About this world
Kepler-1321 d is a sub-Neptune orbiting Kepler-1321, an orange dwarf 2.51 thousand light-years from Earth. It is about 2.6 times the size of Earth. It completes an orbit every 5.72 days at 0.05 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 509 K (236 °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 2021 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-1321 has 3 known planets; the others are Kepler-1321 c and Kepler-1321 b.