Luyten 726-8 (also known as Gliese 65) is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus. Luyten 726-8B is also known under the variable star designation UV Ceti, being the archetype for the class of flare stars.
The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and cataloged it as Luyten 726-8.5 The two stars are of nearly equal brightness, with visual 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 astronomical units (310 to 1,320 Gm). The Luyten 726-8 system is approximately 2.63 parsecs (8.58 ly) from Earth's Solar System, in the constellation Cetus, and is thus the sixth-closest star system to Earth. Its own nearest neighbor is Tau Ceti, 0.88 pc (2.87 ly) away from it. If Rv = + 29 km/s then approximately 28,700 years ago Luyten 726-8 was at its minimal distance of 2.21 pc (7.2 ly) from the Sun.
In approximately 31,500 years, Luyten 726-8 will have a close encounter with Epsilon Eridani at the minimal distance of about 0.93 ly. Luyten 726-8 can penetrate a conjectured Oort cloud about Epsilon Eridani, which may gravitationally perturb some long-period comets. The duration of mutual transit of two star systems within 1 ly from each other is about 4,600 years.
Luyten 726-8 is a possible member of the Hyades Stream.
Luyten 726-8A (BL Ceti)
Luyten-726-8A was found to be a variable star and given the variable star designation BL Ceti.3 It is a red dwarf of spectral type M5.5e. It is also a flare star, and classified as a UV Ceti variable type, but it is not nearly as remarkable or extreme in its behavior as its companion star UV Ceti. BL Ceti is also known as G 272-061.
Luyten 726-8B (UV Ceti)
Soon after the discovery of Luyten 726-8A, the slightly brighter companion star Luyten 726-8B was discovered. Like Luyten 726-8A, this star was also found to be variable and given the variable star designation UV Ceti.4 Although UV Ceti was not the first flare star discovered, it is the most prominent example of such a star, now similar flare stars are classified 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.
UV Ceti in space opera:
- In A Gift from Earth by Larry Niven, the robot ramscoops use the gas cloud around UV Ceti for braking on their way to Tau Ceti.
- In C.J. Cherryh's Alliance-Union future history, UV Ceti is the site of Eldorado Station, one of the stations on the "Great Circle" chain of space stations that terminates at Pell Station in the Tau Ceti system.