Libra constellation lies in the southern sky. It is one of the zodiac constellations, first catalogued by Ptolemy in the 2nd century. The constellation is represented by the symbol ♎. It does not contain any first magnitude stars.
The constellation’s name means “the weighing scales” in Latin, and Libra is usually depicted as the scales held by the Greek goddess of justice Dike (or Astraea), represented by the neighbouring Virgo constellation. Libra is the only zodiac constellation that represents an object, not an animal or a character from mythology. The four brightest stars in the constellation form a quadrangle. Alpha and Beta Librae mark the scales’ balance beam, and Gamma and Sigma Librae represent the weighing pans. Libra is also home to HD 140283, popularly known as Methuselah, currently the oldest known star in the universe.
Legend of Libra Constellation
Ancient Greeks knew the part of the sky occupied by the Libra constellation as Chelae, or “claws,” and considered it part of Scorpio constellation. Chelae represented the scorpion’s claws. The association of this region of the sky with scales was established among the Romans in the first century BC. It is said that Moon was located in Libra when Rome was founded. The Romans considered Libra to be a favoured constellation, one associated with balanced seasons and equal length of night and day. The Sun was at the autumnal equinox in Libra until the year 729, when the precession of the equinoxes shifted the equinox to Virgo. The autumnal equinox will move to constellation Leo in the year 2439.
The Romans were not the first to associate Libra with the idea of balance. The Babylonians called it ZIB.BA.AN.NA, which means “the balance of heaven,” about a thousand years before Christ. Once Libra became associated with balance, its association with Scorpio’s claws faded and the one with the goddess of justice, the Greek Dike or Astraeia, represented by the constellation Virgo, became stronger. As a reminder that Libra was once considered a part of Scorpio constellation, the brightest star in Libra, Beta Librae, has the name Zubeneschamali, which means “the northern claw” in Arabic, while Alpha Librae, Zubenelgenubi, is “the southern claw.”
How to find the constellation Libra in the sky?
Libra takes up a 538 sq/deg area of the sky, with the constellation’s “scale” shape formed by the stars Alpha and Beta Librae that form the “cross-beam”, and the stars Gamma and Sigma Librae that represent the “weighing pans.”
Libra is a southern sky constellation that can be seen by observers located between latitudes of +65° and -90°, although in the northern hemisphere it is best seen in spring and summer, and in the southern hemisphere from autumn to winter. The constellation’s most luminous stars form a quadrangular pattern that can be found between Virgo to its north-west, and Scorpius to its south-east, by using their brightest stars, Spica and Antares respectively as guides. Other neighbouring constellations include Centaurus, Hydra, Ophiuchus, Serpens Caput, and Lupus.
At that time of its creation in Babylon, the Sun’s position in front of the constellation’s stars marked the start of the autumnal equinox, during which time the day and night, being weighed, would be found equal. However, with precession over time the Sun has now moved south of the ecliptic into Virgo, which currently marks the autumn equinox.