About this world
TOI-421 c is a Neptune-like planet orbiting TOI-421, a yellow, Sun-like star (type G9V) 244 light-years from Earth. It is about 5.1 times the size of Earth and holds 14 Earth masses. It completes an orbit every 16.1 days at 0.12 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 635 K (362 °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: 2 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. TOI-421 has 2 known planets; the others are TOI-421 b.