About this world
TOI-270 d is a sub-Neptune orbiting TOI-270, a cool red dwarf (type M3V) 73.3 light-years from Earth. It is about 2 times the size of Earth and holds 4.2 Earth masses. It completes an orbit every 11.4 days at 0.072 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 383 K (110 °C): too cold for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock. Its atmosphere has already been studied: 10 spectroscopic observations, 8 of them with the James Webb Space Telescope.
It was discovered in 2019 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction. TOI-270 has 3 known planets; the others are TOI-270 b and TOI-270 c.