About this world
K2-157 d is a Neptune-like planet orbiting K2-157, a yellow, Sun-like star (type G9V) 973 light-years from Earth. It is about 5.2 times the size of Earth (its size estimated from its mass), with at least 23 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 66.5 days at 0.31 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.5).
Its equilibrium temperature is about 429 K (156 °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 2025 by radial velocity with Paranal Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. K2-157 has 3 known planets; the others are K2-157 b and K2-157 c.