About this world
K2-54 b is a sub-Neptune orbiting K2-54, an orange dwarf 571 light-years from Earth. It is about 2.6 times the size of Earth. It completes an orbit every 9.78 days at 0.076 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.24).
Its equilibrium temperature is about 560 K (287 °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.