Luyten 726-8

Luyten 726-8 (UV Ceti or Gliese 65) is a binary star which is one of Earth's nearest neighbours. It is about 8.7 light years from Earth in the constellation Cetus. One of the pair, UV Ceti, was the archetype for the class of flare stars.
The star system was discovered in 1948 by W.J Luyten in the course of compiling a catalogue of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and catalogued it as Luyten 726-8.
The two stars are of nearly equal brightness, with apparent magnitudes of 12.57 and 11.99 as seen from Earth. They orbit one another every 26.5 years. The distance between the two stars varies from 2.1 to 8.8 AU. Its own nearest neighbour is Tau Ceti, away from it.
Both the stars are variables. The most spectacular is Luyten 726-8B, which was given the variable star designation UV Ceti (the other star is also known as BL Ceti). Although UV Ceti was not the first flare star discovered, it is the most prominent example of such a star, and similar flare stars are now known as UV Ceti type variable stars. This star goes through fairly extreme changes of brightness: for instance, in 1952, its brightness increased by 75 times in only 20 seconds. UV Ceti is a red dwarf of spectral type M6.0e.