Star Tales – Libra

Originally, the area of sky we know as Libra was occupied by the claws of the Scorpion, Scorpius. The Greeks called this area Chelae, literally meaning ‘claws’, an identification that lives on in the names of the individual stars of Libra (see below). As things have worked out, Libra is now a slightly larger constellation than Scorpius, but is much less conspicuous.

The identification of this area with a balance became established in the first century BC among the Romans, although exactly when it was introduced and by whom has been lost in the mists of history. To the Romans, Libra was a favoured constellation. The Moon was said to have been in Libra when Rome was founded. ‘Italy belongs to the Balance, her rightful sign. Beneath it Rome and her sovereignty of the world were founded’, said the Roman writer Manilius. He described Libra as ‘the sign in which the seasons are balanced, and the hours of night and day match each other’. This is a hint that the Romans visualized the constellation as a balance because the Sun lay there at the autumn equinox, when day and night are equal. But the idea of a balance in this area did not originate with the Romans. According to historian Gwyneth Heuter the Sumerians knew this area as ZIB-BA AN-NA, the balance of heaven, 2000 years BC. Hence it seems that the Romans revived a constellation that existed before Greek times.

The balance pans of Libra, depicted in the Atlas Coelestis of John Flamsteed.

Libra is the only constellation of the zodiac to represent an inanimate object; the other 11 zodiacal constellations represent animals or mythological characters. Once the identification of Libra with a pair of scales became established it was natural to divorce it entirely from Scorpius and to associate it instead with the other flanking zodiacal figure, Virgo, who was identified with Dike or Astraeia, goddess of justice. Libra thus became the scales of justice held aloft by the goddess.

Libra’s brightest star, second-magnitude Alpha Librae, is called Zubenelgenubi from the Arabic meaning ‘the southern claw’, a reminder of the Greek identification of this constellation with the claws of the scorpion. Beta Librae is Zubeneschamali, ‘the northern claw’.

In the Chinese sky, the square formed by Alpha, Iota, Gamma and Beta Librae was Di, a palace for the Emperor to stay the night with his wife and two concubines. Di was also the name given to the 3rd Chinese lunar mansion.

Theta and 48 Librae were part of a line of four stars leading into northern Scorpius that formed Xixian, one wall of an area used for investigating and penalizing rogue traders in the celestial market just to the north; the other wall, Dongxian, was in Ophiuchus. In the south of the constellation were a couple of constellations forming part of a large cavalry camp that was envisaged spread over a large area south of the ecliptic. Zenche, consisting of a triangle of stars (probably Sigma Librae and two to the south in Lupus), was a formation of battle chariots, while Tianfu (probably Upsilon and Tau Librae) was a pile of spare spokes for mending broken wheels.

A star in Libra on or close to the ecliptic, near the border with Scorpius, was known as Ri, the Sun star; it lies on the opposite side of the sky from the Moon star, Yue, in Taurus, in recognition that the Sun and full Moon lie opposite each other in the sky. However, the identification of Ri is uncertain; it could be Kappa, Lambda or 42 Librae, all of which are of similar brightness (about magnitude 5.0).