About this world
AU Mic b is a Neptune-like planet orbiting AU Mic, a cool red dwarf (type M1V) 31.7 light-years from Earth. It is about 4.8 times the size of Earth and holds 9 Earth masses. It completes an orbit every 8.46 days at 0.07 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 555 K (282 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium. Its atmosphere has already been studied: 4 spectroscopic observations, all of them with the James Webb Space Telescope.
It was discovered in 2020 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. AU Mic has 4 known planets; the others are AU Mic d, AU Mic c and AU Mic e.