About this world
HD 109271 b is a Neptune-like planet orbiting HD 109271, a yellow, Sun-like star (type G5V) 182 light-years from Earth. It is about 4.3 times the size of Earth (its size estimated from its mass), with at least 17 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 7.85 days at 0.079 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.25).
Its equilibrium temperature is about 1,129 K (856 °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 2013 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 109271 has 2 known planets; the others are HD 109271 c.