About the starAlpha Sagittarii is a blue dwarf belonging to the spectral class B8V. It has an apparent magnitude of 3.97 and is approximately 170 light years distant. The star is believed to have a debris disk, like Vega, the brightest star in the constellation Lyra. What is atypical for a B8V class star is that Alpha Sagittarii is emitting an excess flux of X-rays, possibly because its companion star is still in the pre-main sequence stage. Alpha Sagittarii shares its traditional name, Rukbat, with the star Delta Cassiopeiae (now formally known as Ruchbah). The name is derived from the Arabic word rukbah, which means "knee."In fiction, Rukbat is probably best known from Anne McCaffrey's Dragonriders of Pern series of novels and stories. Pern, the planet on which the action takes place, orbits Rukbat, which is described as a class G yellow star in the novels.Sagittarius MythIn Greek mythology, Sagittarius represents a centaur, a half human, half horse creature with the torso of a man and the body and four legs of a horse. The centaur is depicted as aiming an arrow toward the heart of the neighbouring constellation Scorpio, represented by the red supergiant star Antares. Sometimes Sagittarius is wrongly identified as the centaur Chiron, represented by the constellation Centaurus.Sagittarius constellation has its roots in Sumerian mythology. Eratosthenes associated it with Crotus, a mythical creature with two feet and a satyr's tail, who was the nurse to the nine Muses, daughters of Zeus. Eratosthenes argued that the constellation really represented a satyr and not a centaur. According to the Roman author Hyginus, Crotus was the son of Pan and the archer the constellation was named after. Crotus invented archery and lived on Mount Helicon. Because he was close to the Muses, they were the ones who asked Zeus to place him in the sky.In Babylonian mythology, Sagittarius is associated with the centaur-like god Nergal, and depicted with two heads – one human and one panther – and also wings, and the stinger of a scorpion positioned above a horse's tail.