Luyten 726-8 (UV Ceti) is one of the nearest star systems to the Sun at a distance of 8.73 light-years (see stars, nearest). It lies in the constellation Cetus, northeast of Deneb Kaitos (Beta Ceti). Luyten 726-8 is a binary in which both components are red dwarfs in a highly elliptical orbit of period 26.5 years that takes the two stars between 2.1 and 8.8 AU apart. Component B is an extreme example of a flare star that can surge in brightness by a factor of five in less than a minute, then fall somewhat slower back down to normal luminosity within two or three minutes before flaring suddenly again after several hours. In 1952, Luyten 726-8 B, better known by its variable-star name UV Ceti, was observed flaring to 75 times its normal brightness in only 20 sec. It is the prototype of the class known as UV Ceti stars.

 

	type	mass (Sun=1)	luminosity (Sun=1)	radius (Sun=1)
A	M5.5eV	0.10	0.15	0.000011
B	M6eV	0.10	0.14	0.000004