About

Libra is a constellation of the zodiac and is located in the Southern celestial hemisphere. Its name is Latin for weighing scales. Its old astronomical symbol is (♎︎). It is fairly faint, with no first magnitude stars, and lies between Virgo to the west and Scorpius to the east. Beta Librae, also known as Zubeneschamali, is the brightest star in the constellation. Three star systems are known to have planets.

History and mythology

Libra was known in Babylonian astronomy as MUL Zibanu (the "scales" or "balance"), or alternatively as the Claws of the Scorpion. The scales were held sacred to the sun god Shamash, who was also the patron of truth and justice. Since these times, Libra has been associated with law, fairness and civility. It was also seen as the Scorpion's Claws in ancient Greece. This is the name used repeatedly by Aratus, which made it widespread in Hellenistic times: "few conspicuous stars the Claws can boast, and their dim light mid brighter gems is lost" In Arabic zubānā means "scorpion's claws", and likely similarly in other Semitic languages: this resemblance of words may be why the Scorpion's claws became the Scales. Indeed, Zubenelgenubi and Zubeneschamali, the names of the constellation's two main stars, in Arabic mean "southern claw" and "northern claw" respectively. It has also been suggested that the scales are an allusion to the fact that when the sun entered this part of the ecliptic at the autumnal equinox, the days and nights are equal. Libra's status as the location of the equinox earned the equinox the name "First Point of Libra", though this location ceased to coincide with the constellation in 730 BC because of the precession of the equinoxes. In ancient Egypt the three brightest stars of Libra (α, β, and σ Librae) formed a constellation that was viewed as a boat. Libra is not mentioned by Eudoxus or Aratus as a constellation. Libra is mentioned by Manetho (3rd century B.C.) and Geminus (1st century B.C.), and included by Ptolemy in his 48 asterisms. Ptolemy catalogued 17 stars, Tycho Brahe 10, and Johannes Hevelius 20. It only became a constellation in ancient Rome, when it began to represent the scales held by Astraea, the goddess of justice, associated with Virgo in the Greek mythology.