Luyten << LOW tihn >> 726-8 ranks as the eighth closest star to Earth. The star lies about 8.7 light-years away. One light-year equals the distance light travels in a vacuum in a year, about 9.46 trillion kilometers. As seen from Earth, Luyten 726-8 lies in the southwestern part of the constellation Cetus, the Whale. The Dutch-born astronomer Willem J. Luyten first cataloged the star in 1948.
Luyten 726-8 is a binary star, consisting of two stars—Luyten 726-8 A and Luyten 726-8 B—that revolve around each other. Astronomers classify both stars as small, faint stars called red dwarfs. Each has about 1/10 the mass (amount of matter) of the sun. The diameter of each star also measures about 1/10 that of the sun. Their reddish color results from relatively low surface temperatures, around 2500 K. One kelvin (K) equals one Celsius degree above absolute zero (–273.15 °C). Because of their small size and cool surfaces, the two stars give off a total of about 1/700 as much light as does the sun. They cannot be seen with the unaided eye.
Both stars are variable stars, stars that vary periodically in brightness or magnitude. Astronomers use a special naming system when discussing variable stars. Under this system, they refer to Luyten 726-8 A as BL Ceti and to Luyten 726-8 B as UV Ceti. Both stars are also flare stars, stars that exhibit sudden, intense increases in brightness that fade within a few minutes. UV Ceti exhibits particularly pronounced flares. In less than one minute, it can increase to five times its normal brightness.
