About this world
K2-4 b is a sub-Neptune orbiting K2-4, an orange dwarf 756 light-years from Earth. It is about 2.1 times the size of Earth. It completes an orbit every 10 days at 0.078 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 563 K (290 °C): far too hot for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock.
It was discovered in 2015 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction.