About this world
HD 15906 b is a sub-Neptune orbiting HD 15906, an orange dwarf (type KV) 149 light-years from Earth. It is about 2.2 times the size of Earth. It completes an orbit every 10.9 days at 0.09 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 668 K (395 °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 transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. HD 15906 has 2 known planets; the others are HD 15906 c.