About this world
HD 160691 d is a sub-Neptune orbiting HD 160691, a yellow, Sun-like star (type G3IV-V) 50.9 light-years from Earth. It is about 3.2 times the size of Earth (its size estimated from its mass), with at least 10 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 9.64 days at 0.095 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 900 K (627 °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 2004 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 160691 has 4 known planets; the others are HD 160691 e, HD 160691 b and HD 160691 c.