Astronomers have discovered an Earth-size exoplanet, SPECULOOS-3 b, 55 light-years away, orbiting an ultracool red dwarf star.

This discovery is only the second planetary system found around a red dwarf, following the Trappist-1 system.

SPECULOOS-3 b was identified by the SPECULOOS project, which searches for rocky exoplanets around nearby ultracool stars.

Despite being Earth-size, SPECULOOS-3 b has a rapid orbit with a year lasting just 17 hours and is likely tidally locked.

Red dwarfs like SPECULOOS make up 70% of the Milky Way's stars and have long lifetimes, but SPECULOOS-3 b is inhospitable due to high radiation.

The discovery is significant for the future study of red dwarf worlds, especially with the James Webb Space Telescope to assess atmosphere retention on such close-orbiting planets.

Findings were reported in Nature Astronomy on May 15, 2024, and while SPECULOOS-3 b is not habitable, it advances our knowledge of planetary characteristics in extreme environments.