About this world
TOI-561 d is a sub-Neptune orbiting TOI-561, a yellow, Sun-like star (type G9V) 280 light-years from Earth. It is about 2.6 times the size of Earth and holds 13 Earth masses. It completes an orbit every 25.7 days at 0.16 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 600 K (327 °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 2020 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. TOI-561 has 4 known planets; the others are TOI-561 b, TOI-561 c and TOI-561 e.