About this world
HD 187123 b is a gas giant orbiting HD 187123, a yellow, Sun-like star (type G3V) 150 light-years from Earth. It is about 1.3 times the size of Jupiter (its size estimated from its mass), with at least 0.52 Jupiter masses (a minimum, measured by radial velocity). It completes an orbit every 3.1 days at 0.043 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,451 K (1,178 °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 1998 by radial velocity with W. M. Keck Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 187123 has 2 known planets; the others are HD 187123 c.