About this world
TOI-521 b is a super-Earth orbiting TOI-521, a cool red dwarf (type M3) 199 light-years from Earth. It is about 2 times the size of Earth and holds 5.3 Earth masses. It completes an orbit every 1.54 days at 0.019 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 794 K (521 °C): far too hot for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock.
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.