About this world
GJ 3942 b is a sub-Neptune orbiting GJ 3942, a cool red dwarf (type M0) 55.2 light-years from Earth. It is about 2.6 times the size of Earth (its size estimated from its mass), with at least 7.1 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 6.91 days at 0.061 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 590 K (317 °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 2017 by radial velocity with Roque de los Muchachos Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.