About this world
HD 171238 b is a gas giant orbiting HD 171238, a yellow, Sun-like star (type G8V) 146 light-years from Earth. It is about 1.1 times the size of Jupiter (its size estimated from its mass) and holds 8.8 Jupiter masses. It completes an orbit every 4.15 years at 2.5 AU from its star, on a strongly elongated orbit (e = 0.36).
Its equilibrium temperature is about 167 K (−106 °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 2009 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.