About this world
HD 219828 b is a Neptune-like planet orbiting HD 219828, a yellow, Sun-like star (type G0IV) 238 light-years from Earth. It is about 4.6 times the size of Earth (its size estimated from its mass), with at least 19 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 3.83 days at 0.049 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,603 K (1,330 °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 2007 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 219828 has 2 known planets; the others are HD 219828 c.