About this world
GJ 357 d is a sub-Neptune orbiting GJ 357, a cool red dwarf (type M2.5V) 30.8 light-years from Earth. It is about 2.3 times the size of Earth (its size estimated from its mass), with at least 6.1 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 55.7 days at 0.2 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 220 K (−54 °C), which places it in the conservative habitable zone: the band where liquid water could exist on a rocky surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2019 by radial velocity with Multiple Observatories. The star wobbles toward and away from us, Doppler-shifting its spectrum. GJ 357 has 3 known planets; the others are GJ 357 b and GJ 357 c.