About this world
K2-28 b is a sub-Neptune orbiting K2-28, a cool red dwarf (type M4) 205 light-years from Earth. It is about 2.3 times the size of Earth. It completes an orbit every 2.26 days at 0.021 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 568 K (295 °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 K2. A planet crosses its star and dims it by a tiny, periodic fraction.