About this world
WASP-166 b is a Neptune-like planet orbiting WASP-166, a yellow-white F-type star (type F9V) 372 light-years from Earth. It is about 0.63 times the size of Jupiter and holds 0.1 Jupiter masses. It completes an orbit every 5.44 days at 0.064 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,270 K (997 °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 2019 by transit with WASP-South. A planet crosses its star and dims it by a tiny, periodic fraction.