About this world
Kepler-538 b is a sub-Neptune orbiting Kepler-538, a yellow, Sun-like star 509 light-years from Earth. It is about 2.2 times the size of Earth and holds 13 Earth masses. It completes an orbit every 81.7 days at 0.36 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.21).
Its equilibrium temperature is about 417 K (144 °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 2016 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction.