About this world
TOI-199 b is a Neptune-like planet orbiting TOI-199, a yellow, Sun-like star (type G9V) 334 light-years from Earth. It is about 0.81 times the size of Jupiter and holds 0.17 Jupiter masses. It completes an orbit every 105 days at 0.43 AU from its star.
Its equilibrium temperature is about 325 K (52 °C): too cold 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: 3 spectroscopic observations, all of them with the James Webb Space Telescope.
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. TOI-199 has 2 known planets; the others are TOI-199 c.