About this world
HD 224018 c is a sub-Neptune orbiting HD 224018, a yellow, Sun-like star (type GV) 344 light-years from Earth. It is about 2.4 times the size of Earth and holds 10 Earth masses. It completes an orbit every 36.6 days at 0.22 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 641 K (368 °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 2025 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction. HD 224018 has 3 known planets; the others are HD 224018 b and HD 224018 d.