About this world
Kepler-20 d is a sub-Neptune orbiting Kepler-20, a yellow, Sun-like star 922 light-years from Earth. It is about 2.6 times the size of Earth and holds 13 Earth masses. It completes an orbit every 77.6 days at 0.35 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 430 K (157 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium. Its atmosphere has already been studied: 2 spectroscopic observations.
It was discovered in 2011 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-20 has 6 known planets; the others are Kepler-20 b, Kepler-20 e, Kepler-20 c, Kepler-20 f and Kepler-20 g.