About this world
TOI-4438 b is a sub-Neptune orbiting TOI-4438, a cool red dwarf (type M3.5V) 98 light-years from Earth. It is about 2.4 times the size of Earth and holds 4.1 Earth masses. It completes an orbit every 7.45 days at 0.052 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 446 K (173 °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.
It was discovered in 2024 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction.