About this world
K2-12 b is a sub-Neptune orbiting K2-12, a yellow-white F-type star (type F9) 1.06 thousand light-years from Earth. It is about 2.4 times the size of Earth and holds 5.2 Earth masses. It completes an orbit every 8.28 days at 0.079 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.5).
Its equilibrium temperature is about 1,026 K (753 °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 2015 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction.