About this world
HD 176986 d is a sub-Neptune orbiting HD 176986, an orange dwarf (type K2.5V) 90.6 light-years from Earth. It is about 2.5 times the size of Earth (its size estimated from its mass), with at least 6.8 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 61.4 days at 0.28 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 363 K (90 °C): too cold for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2026 by radial velocity with Multiple Observatories. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 176986 has 3 known planets; the others are HD 176986 b and HD 176986 c.