About this world
TOI-5543 b is a sub-Neptune orbiting TOI-5543, an orange dwarf 408 light-years from Earth. It is about 3.8 times the size of Earth. It completes an orbit every 3.54 days at 0.043 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 994 K (721 °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 2026 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction.