About this world
HD 31527 d is a sub-Neptune orbiting HD 31527, a yellow, Sun-like star (type G2V) 125 light-years from Earth. It is about 3.5 times the size of Earth (its size estimated from its mass), with at least 12 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 272 days at 0.81 AU from its star, on a strongly elongated orbit (e = 0.24).
Its equilibrium temperature is about 327 K (54 °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 2019 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 31527 has 3 known planets; the others are HD 31527 b and HD 31527 c.