About this world
HD 18438 b is a gas giant orbiting HD 18438, a giant star (type M2.5III) 731 light-years from Earth. It is about 1.1 times the size of Jupiter (its size estimated from its mass), with at least 21 Jupiter masses (a minimum, measured by radial velocity). It completes an orbit every 2.2 years at 2.1 AU from its star.
Its equilibrium temperature is about 1,208 K (935 °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 2023 by radial velocity with Bohyunsan Optical Astronomical Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum.