About this world
TOI-663 b is a sub-Neptune orbiting TOI-663, a cool red dwarf (type M1V) 209 light-years from Earth. It is about 2.3 times the size of Earth and holds 4.5 Earth masses. It completes an orbit every 2.6 days at 0.029 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 674 K (401 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
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. TOI-663 has 3 known planets; the others are TOI-663 c and TOI-663 d.