An ultra-cool dwarf is a stellar or sub-stellar object of spectral class M that has an effective temperature under 2,700 K (2,430 °C; 4,400 °F). TRAPPIST-1 is one of the best known examples of an ultra-cool dwarf star. – Image credit: ESO/M. Kornmesser

Related channels: TRAPPIST-1 SYSTEM, STARS, EXOPLANETSKEPLER SPACE TELESCOPE, SPITZER SPACE TELESCOPESETI INSTITUTE, SPACE COLONIZATIONALPHA CENTAURI, THE MILKY WAYRADIO ASTRONOMY