About this world
GJ 1289 b is a sub-Neptune orbiting GJ 1289, a cool red dwarf (type M4.5VE) 27.2 light-years from Earth. It is about 2.4 times the size of Earth (its size estimated from its mass), with at least 6.3 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 112 days at 0.27 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 150 K (−123 °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 2024 by radial velocity with Multiple Observatories. The star wobbles toward and away from us, Doppler-shifting its spectrum.