About this world
TOI-1117 c is a sub-Neptune orbiting TOI-1117, a yellow, Sun-like star (type G5V) 547 light-years from Earth. It is about 2.9 times the size of Earth (its size estimated from its mass), with at least 8.8 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 4.58 days at 0.053 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,210 K (937 °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 radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. TOI-1117 has 3 known planets; the others are TOI-1117 b and TOI-1117 d.