Libra is a zodiac constellation that can be found in the southern hemisphere of the sky. Its name comes from the Latin word for scales. Libra is its old astronomical symbol is a vector graphic format. It sits between Virgo to the west and Scorpius to the east and is fairly dim with no first magnitude stars. The brightest star in the constellation is Beta Librae, also known as Zubeneschamali. Planets have been discovered in three-star systems.
Libra is bounded to the north by the head of Serpens, to the northwest by Virgo, to the southwest by Hydra, to the southwest by the corner of Centaurus, to the south by Lupus, to the east by Scorpius, and to the northeast by Ophiuchus. It is the 29th largest constellation, covering 538.1 square degrees and 1.304 percent of the night sky. The International Astronomical Union selected the three-letter acronym "Lib" for the constellation in 1922. (Russell 1922) A polygon of twelve segments defines the official constellation borders, which were established by Eugène Delporte in 1930. The right ascension coordinates of these borders are between 14h 22m 08.08s and 16h 02m 17.23s in the equatorial coordinate system, while the declination values are between 0.47° and 30.00°. The entire constellation is visible to observers south of latitude 60°N. |
History and Mythology
In Babylonian astronomy, Libra was known as MUL Zibanu (the "scales" or "balance"), or the Claws of the Scorpion. The sun deity Shamash, who was also the guardian of truth and justice, was revered for the scales. In ancient Greece, it was also known as the Scorpion's Claws. (Ridpath & Tirion 2001) Libra has been connected with law, fairness, and civility since ancient times. In Arabic, zubn means "scorpion's claws," and other Semitic languages may have similar meanings: this similarity of words may explain why the Scorpion's claws became the Scales. The names of the constellation's two major stars, Zubenelgenubi and Zubeneschamali, respectively, represent "southern claw" and "northern claw" in Arabic. The scales may allude to the fact that the days and nights are equal when the sun enters this portion of the ecliptic at the autumnal equinox. (Chisholm 1911) The equinox was given the name "First Point of Libra" because of its placement in Libra, yet due to equinox precession, its point no longer coincided with the constellation around 730 BC. The three brightest stars of Libra (α, β, and σ Librae) created a constellation that was perceived as a boat in ancient Egypt. Eudoxus and Aratus do not mention Libra as a constellation. Manetho (third century B.C.) and Geminus (first century B.C.) both mention Libra, and Ptolemy included it in his forty-eight asterisms. Ptolemy identified seventeen stars, Tycho Brahe identified ten, and Johannes Hevelius identified twenty. (Chisholm 1911) It was only in ancient Rome that it became a constellation when it began to represent the scales wielded by Astraea, the goddess of justice connected with the constellation Virgo in Greek mythology. (Ridpath & Tirion 2001) |
Deep-space Objects
NGC 5897 – Ghost Globular Cluster - Globular Cluster
IC 1059 - linear Galaxy
Libra also has several small galaxies within the constellation which require a large aperture telescope to see.
Bayer stars - 56
Stars with planets - 4
Stars brighter than magnitude 3.00 - 2
Stars within 32 Ly - 5
Bordering
constellations
NGC 5897 – Ghost Globular Cluster - Globular Cluster
IC 1059 - linear Galaxy
Libra also has several small galaxies within the constellation which require a large aperture telescope to see.
Bayer stars - 56
Stars with planets - 4
Stars brighter than magnitude 3.00 - 2
Stars within 32 Ly - 5
Bordering
constellations
- Serpens Caput
- Virgo
- Hydra
- Centaurus (corner)
- Lupus
- Scorpius
- Ophiuchus