About this world
GJ 338 B b is a sub-Neptune orbiting GJ 338 B, a cool red dwarf (type M0V) 20.7 light-years from Earth. It is about 3.3 times the size of Earth (its size estimated from its mass), with at least 11 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 24.4 days at 0.14 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 391 K (118 °C): too cold for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2020 by radial velocity with Calar Alto Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.