Libra is the only sign of the zodiac that is not a living creature. It is a pair of scales, and its history is a tug of war between two pictures, a pair of scales and a pair of claws.
The claws
The Babylonians saw a pair of scales in these stars as early as about 1000 BCE. The early Greeks, though, saw the claws of the neighboring Scorpion. The Greek name for the area was Chelae, "the claws," and the astronomer Hipparchus and the later writer Ptolemy still used it. The Romans brought the scales back, probably around the first century BCE. The change is linked to the autumn equinox, when the sun crossed the celestial equator in this part of the sky and day and night were balanced. The Roman poet Virgil described the scales weighing the hours of day and night.
Old names, new picture
The fossil of the older picture survives in the stars' names. Libra's two brightest stars are Zubenelgenubi and Zubeneschamali, from the Arabic for "the southern claw" and "the northern claw." Astronomers kept the names even after the claws turned into the pans of a balance.
Justice in the sky
The scales are tied to the next-door constellation Virgo, who in one story is the goddess of justice, Astraea, and the scales are the ones she held. In Egyptian belief the dead had their hearts weighed against the feather of truth, and in astrology Libra is ruled by Venus and stands for harmony and fairness.
How to find it
Libra sits in the south in summer evenings, halfway between Spica in Virgo and red Antares in Scorpius. Its stars form a lopsided box, with Zubeneschamali, the faint greenish one, at the top. Nothing in it is dazzling, and it rewards patience more than a quick look.
On the star chart
On the card the scales are drawn with the beam tilted and two wide yellow pans, and they are set against the stars that once belonged to the Scorpion's claws.
Little-known facts
- Libra has no star brighter than about magnitude 2.6, so it is a pale constellation.
- The Sun reaches the autumn equinox in Virgo now, not Libra, because of precession.
- Gliese 581, a red dwarf in Libra, drew headlines in 2007 when astronomers found planets around it, including one that was first reported as possibly habitable.
- The scales appear on the emblems of law courts around the world, but the blindfold is a later addition.
Libra appears on our:
