Star Constellation Facts: Libra the Scales

Star Constellation Facts: Libra, the Scales
Image Credit: Alexander Jamieson’s Celestial Atlas (1822) - Public Domain

Libra is a faint constellation that is the 29th biggest in the night sky, and the only zodiac sign not to represent a living creature. Instead, Libra is depicted in the heavens as “weighing scales” placed next to the hand of its neighboring constellation Virgo, a goddess of justice who had scales as an emblem of her office. The measuring symbol for pounds (“lb”) is an abbreviation of the word Libra.

Libra constellation symbolism and myth

The constellation’s association with scales is thought to have originated in ancient Babylonia around 2000 BC, where Libra was called ZIB.BA.AN.NA (“the balance of heaven”). In ancient Greece, Libra was considered to be part of the constellation Scorpius, and represented the creature’s claws, and was noted as such by Ptolemy in his astronomical catalog Almagest around AD 150. During the reign of Roman dictator Julius Caesar, however, the constellation Libra was created, and was envisioned as scales held by Astraea, the goddess of justice, although its two brightest stars still retained their original names; Zubeneschamali (The Northern Claw), and Zubenelgenubi (The Southern Claw).

Located between the bright stars Spica and Antares

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 northwest, and Scorpius to its southeast, by using their brightest stars, Spica and Antares respectively as guides. Other neighboring star constellations include Centaurus, Hydra, Ophiuchus, Serpens Caput, and Lupus.

Major stars in the Libra constellation

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 Virgo Scorpius

Zubeneschamali (Beta Librae), the most luminous star in Libra, is located about 185 light years away, and shines with an apparent magnitude of 2.61. The star is a blue-white dwarf (B8 V) around 5 times as big as the Sun, and at least 130 times as luminous. It is also a fast rotator, with a rotational velocity of about 250 km/sec at its equator. Beta Librae is thought to be a binary star since small, periodic variations in brightness have been observed, but to date, no companion has been identified.

– Zubenelgenubi (Alpha Librae), the second most luminous star in Libra, is a binary system found 75 light years from our solar system that shines with an apparent magnitude of 5.153. Alpha Librae forms the primary pair of the system, and both stars are thought to be members of the Castor Moving Group of stars, since they share a common proper motion, which implies a common origin about 200 million years ago.

Other stars of interest in Alpha Librae include the blue supergiant 48 Librae, the blue-white dwarf stars Tau Librae and Zuben Elakribi (Delta Librae); the yellow dwarf stars 23 Librae and HD 141937; the orange giant stars Upsilon Librae, Gamma Librae, Zuben Elakrab, and Theta Librae; and the red giant Brachium, and the red dwarf star Gliese 581.

Libra contains the oldest star in the Universe

Libra contains the oldest know star ever discovered, aptly named after the person with the longest lifespan in the Bible. The star Methuselah (HD 140283) is located 190 light years from our Sun, and is a seventh-magnitude star that is currently in its pre-red giant phase. It is also the oldest known star, with an estimated age of about 14.46 billion years, give or take 800 million years or so. At first glance, the star’s age seems to contradict the age of the Universe, which is estimated to be about 13.77 billion years old, but the huge uncertainties in the ages of both the star and the Universe means that there is no real conflict. Methuselah consists almost entirely of hydrogen and helium, with only trace amounts of heavy atoms, which means that the star is among the oldest surviving second-generation stars.

Notable objects include galaxies, globular cluster

There may not be a plethora of notable deep sky objects in Libra, but it does contain the globular cluster NGC 5897, which is 170 light-years wide, 24,000 light-years distant, and shines with an apparent magnitude of 8.5. In Libra can also be found the barred spiral galaxies NGC 5792 and NGC 5885; and the lenticular galaxy NGC 5890. All these objects, however, can only be seen in large telescopes.

Libra associated with May Librids meteor shower

The May Librids, the only meteor shower associated with the constellation Libra, was apparently first noticed on May 5, 1929, by members of the American Meteor Society. The meteor shower has a very short duration period that runs from May 1st to 9th, with its peak on the 6th, during which time a maximum of 2 to 6 meteors per hour can be seen.

Libra has 3 stars with confirmed planets

Of the four IAU-named stars in Libra three have confirmed planets. One of the most interesting is Gliese 581, a red dwarf star some 20 light years away. It has more than four confirmed planets, including Gliese 581, which is located in the star’s habitable zone, and is now considered one of the most promising planets yet discovered for extra-solar life or human habitability.

Libra astrological sign and association

At the time of Libra’s creation in Babylon, the Sun’s position in front of its pattern of 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.

  • Date of Birth: Sept 23 to Oct 23
  • Sign Ruler: Venus
  • Element: Air
  • Birth Stone: Coral, Amber
  • Metal: Quicksilver
  • Color: Brown
  • Characteristics: Idealistic, fair-minded, strong social skills, charming, artistic
  • Compatibility: Aquarius, Gemini and Libra

Related Posts

Related Posts