About this world
HD 99109 b is a gas giant orbiting HD 99109, a yellow, Sun-like star (type G8/K0IV) 179 light-years from Earth. It is about 1.3 times the size of Jupiter (its size estimated from its mass), with at least 0.44 Jupiter masses (a minimum, measured by radial velocity). It completes an orbit every 439 days at 1.1 AU from its star.
Its equilibrium temperature is about 239 K (−34 °C), which places it in the conservative habitable zone: the band where liquid water could exist on a rocky surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2005 by radial velocity with W. M. Keck Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.