One summer constellation with an interesting history is the star pattern known as Libra the Scales. On a warm summer evening it can viewed toward the southern horizon near the reddish star Antares. That star is in Scorpius and in ancient times Libra was also a part of the constellation Scorpius. Libra served as the claws of the scorpion and the two brightest stars in Libra are still called the Northern Claw and the Southern Claw.

The Romans were known for many things including their system of laws. It was the Romans who removed the claws from the scorpion and created a new constellation in the night sky. This constellation was meant to represent the scales of justice. In the northern hemisphere Libra is the only figure within the zodiac that represents a man-made object.

Libra was added to the zodiac during the time of Julius Caesar. Caesar established a new calendar called, appropriately enough, the Julian calendar. Caesar’s new calendar remained in use for almost 1600 years. It was replaced by the Gregorian calendar which was promoted by Pope Gregory in the 1580s. This is the calendar we use today. Interestingly Libra is often associated with the nearby constellation of Virgo. The Romans viewed Virgo as a goddess of justice so having the scales of justice nearby is appropriate.

Libra is “home” to the Gliese 581 planetary system. A number of exoplanets have been found within the Gliese 581 system including Gliese 581c which was the first Earth-scale exoplanet found within another star’s habitable zone. Gliese 581c has a number of companion worlds that circle the parent star. Perhaps these could be named after prominent Romans?

libra2
Constellation Libra with diagram and stars labelled.

(Images may be found at Professor James Kaler’s website at the University of Illinois: http://stars.astro.illinois.edu)

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