About this world
HD 217786 c is a sub-Neptune orbiting HD 217786, a yellow-white F-type star (type F8V) 181 light-years from Earth. It is about 2.6 times the size of Earth (its size estimated from its mass), with at least 7.3 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 2.52 days at 0.038 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.4).
Its equilibrium temperature is about 1,663 K (1,390 °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 2022 by radial velocity with Multiple Observatories. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 217786 has 2 known planets; the others are HD 217786 b.