About this world
HD 39855 b is a sub-Neptune orbiting HD 39855, a yellow, Sun-like star (type G8V) 75.9 light-years from Earth. It is about 2.9 times the size of Earth (its size estimated from its mass), with at least 8.5 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 3.25 days at 0.041 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,146 K (873 °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 2019 by radial velocity with Las Campanas Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.