About this world
HIP 9618 c is a sub-Neptune orbiting HIP 9618, a yellow, Sun-like star 220 light-years from Earth. It is about 3.4 times the size of Earth and holds 7 Earth masses. It completes an orbit every 52.6 days at 0.27 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 470 K (197 °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 2023 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. HIP 9618 has 2 known planets; the others are HIP 9618 b.