About this world
Kepler-178 d is a sub-Neptune orbiting Kepler-178, a yellow, Sun-like star 2.34 thousand light-years from Earth. It is about 4 times the size of Earth. It completes an orbit every 96.7 days at 0.4 AU from its star.
Its equilibrium temperature is about 392 K (119 °C): too cold for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2014 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-178 has 3 known planets; the others are Kepler-178 b and Kepler-178 c.