About this world
Kepler-223 d is a Neptune-like planet orbiting Kepler-223, a yellow, Sun-like star 6.07 thousand light-years from Earth. It is about 5.2 times the size of Earth and holds 8 Earth masses. It completes an orbit every 14.8 days at 0.12 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 827 K (554 °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 2014 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-223 has 4 known planets; the others are Kepler-223 b, Kepler-223 c and Kepler-223 e.