About this world
HD 90156 b is a Neptune-like planet orbiting HD 90156, a yellow, Sun-like star (type G5V) 71.6 light-years from Earth. It is about 4.4 times the size of Earth (its size estimated from its mass), with at least 18 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 49.8 days at 0.25 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.31).
Its equilibrium temperature is about 518 K (245 °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 2011 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.