About this world
TOI-1803 c is a Neptune-like planet orbiting TOI-1803, an orange dwarf 389 light-years from Earth. It is about 4.3 times the size of Earth and holds 8 Earth masses. It completes an orbit every 12.9 days at 0.097 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 588 K (315 °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 2025 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. TOI-1803 has 2 known planets; the others are TOI-1803 b.