The zodiacal constellation Libra the Scales is a fixture of the evening sky during a Northern Hemisphere summer (Southern Hemisphere winter). It’s not the most flamboyant constellation of the zodiac. But, in any year, you can find Libra fairly easily in a dark sky using two bright stars, Spica and Antares, as guides. Use these two bright stars to find two fainter stars in Libra, which, by the way, have two of the best star names in the sky. Follow the links below to learn more.
By the way, many have noticed that Zubenelgenubi and Zubeneschamali sound a lot like Obi-Wan Kenobi, one of only four characters to appear in all six Star Wars films. Did George Lucas use these stars as inspiration for the character’s name? It would be interesting to know.
As seen from Earth, the sun passes in front of the constellation Libra from about October 30 until November 22 every year.
Libra’s star Zubenelgenubi sits almost exactly on the ecliptic, which is the sun’s yearly path in front of the background stars. At present, the sun has its annual conjunction with the Libra star Zubenelgenubi on or near November 7, or about midway between the September equinox and the December solstice.
However, the conjunction date of the sun and Zubenelgenubi changes over the long course of time.
Over three thousand years ago, the sun and Libra’s star Zubenelgenubi were in conjunction on the Northern Hemisphere’s autumnal equinox (Southern Hemisphere’s spring equinox). Over three thousand years into the future, the sun and Zubenelgenubi will be in conjunction on the December solstice (Northern Hemisphere’s winter solstice or Southern Hemisphere’s summer solstice).
Irrespective of which constellation provides a backdrop for the sun on the September equinox, the sun is said to be at the first point of (the sign) Libra when it the crosses the celestial equator going from north to south.
Libra in history and myth. Several thousands of years ago – around 2,000 B.C. – the ancient Babylonians apparently associated this constellation with scales or a balance. Quite possibly, this association was made because the sun on the autumn equinox shone in front of the stars of Libra at that time. It’s at the equinox that the world realizes its seasonal and temporal balance, between the extremes of heat and cold, and with day and night of equal length all over the globe. Metaphorically, Libra the Scales serves as an age-old symbol of divine justice, harmony and balance.
In contrast to their Babylonian forebears, the ancient Greeks seemed to regard Libra as the outstretched claws of the constellation Scorpius the Scorpion. In fact, the names for Libra’s two brightest stars are Arabic terms that harken back to these olden times when Scorpius reigned as a double or super constellation. Zubenelgenubi translates into “the southern claw of the Scorpion” and Zubeneschamali into “the northern claw of the Scorpion.”
The Romans, though inheriting much of the Greek tradition, again revived Libra as the only inanimate constellation of the Zodiac. In Roman thought, the constellation Virgo is the embodiment of Astraea, the Starry Goddess, holding Libra, the Scales of Justice.
Astrologers regard Libra as the second air sign, ruled over by the planet Venus. Although astronomy and astrology have been intertwined historically, they are now regarded as separate disciplines. Astrology assumes the positions of heavenly bodies have certain influences over human affairs which most modern-day astronomers regard as unfounded.
Bottom line: Libra the Scales – a constellation of the zodiac – can be found in the evening sky during Northern Hemisphere summer (Southern Hemisphere winter). It’s situated between two bright stars, Spica and Antares. Libra’s two brightest stars are Zubenelgenubi and Zubeneschamali, whose names rhyme with Obi-Wan Kenobi of the movie Star Wars.
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Libra? Here’s your constellation
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Birthday late November to early December? Here’s your constellation
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.