Sirius

Sirius, Alpha Canis Majoris (Dog Star), brightest star in the night sky. About 8.8 light years distant from the earth, it is 20 times more luminous than the sun and has an absolute magnitude of + 1.4. A double star, its major component is twice the size of the sun; its major component (the Pup), the first white-dwarf star to be discovered, has a diameter only 50% greater than that of the earth but is extremely dense, its mass being just less than that of the sun.

See also: Binary star.