About this world
K2-25 b is a sub-Neptune orbiting K2-25, a cool red dwarf (type M4.5V) 147 light-years from Earth. It is about 3.4 times the size of Earth and holds 25 Earth masses. It completes an orbit every 3.48 days at 0.029 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.43).
Its equilibrium temperature is about 494 K (221 °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: 4 spectroscopic observations.
It was discovered in 2015 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction.