Libra is one of the less conspicuous constellations of the zodiac, lying between Virgo and Scorpius. Yet it has one distinction none of the other zodiac constellations can claim: it is the only one represented by an inanimate object—the Scales.
Its two brightest stars also have names meaning the “Northern Claw” and “Southern Claw,” preserving a clue to an older identity connected with neighboring Scorpius. Elsewhere in the constellation lies HD 140283, the famous “Methuselah Star,” one of the most ancient stars astronomers have studied.
Libra Sits Between Two Brilliant Stars
Libra is best seen from the Northern Hemisphere during late spring and early summer, with May and June particularly good months for finding it in the evening sky. From the Southern Hemisphere, it is well placed during the corresponding autumn and early winter months. The constellation is visible from roughly 65° north to 90° south.
Because Libra contains no especially bright stars, the easiest way to find it is to use brighter landmarks nearby. One useful route begins with the Big Dipper, or Plough. Follow the curve of its handle to bright orange Arcturus, then continue the same curve until you reach blue-white Spica in Virgo. Once you’ve found Spica, look farther east toward reddish Antares in Scorpius. Libra lies in the comparatively faint region between the two.
Once you’re in the right area, look for Libra’s brighter stars forming a loose four-sided pattern. Traditional constellation diagrams use these stars to trace a weighing balance, although you’re unlikely to look up and immediately see a pair of scales.
Libra’s Brightest Pair: One Looks Green, the Other’s a Double
The brightest star in Libra is Zubeneschamali (Beta Librae), a hot, blue-white star about 185 light-years away. The Bayer designation can initially seem backwards: despite being labeled Beta, Zubeneschamali is brighter than Alpha Librae.
Zubeneschamali also has a curious reputation for appearing pale green or emerald to some observers, even though physically it is blue-white. Stars don’t normally appear truly green because they emit light across a broad range of visible wavelengths rather than concentrating it in green alone. Its reported green tint is therefore an apparent color rather than the star’s true physical color.
Libra’s second-brightest star, Zubenelgenubi (Alpha Librae), is much closer to us at roughly 75 light-years away. To the unaided eye it appears as a single point of light, but binoculars can separate it into two stars, making it an easy double-star target.
The names of the pair are even more intriguing. Zubeneschamali means the “Northern Claw,” while Zubenelgenubi means the “Southern Claw.” Those names seem strangely out of place in a constellation representing a pair of weighing scales. The explanation lies in Libra’s long relationship with the Scorpion next door.
Libra’s Stars Once Formed the Scorpion’s Claws
In Greek astronomical tradition, Libra wasn’t always pictured as a separate pair of Scales. The stars in this part of the zodiac were commonly regarded as the claws of neighboring Scorpius, effectively making the Scorpion a much larger figure than the constellation we recognize today.
The story isn’t simply that the Romans later invented Libra by cutting the claws away from Scorpius. A Balance or Scales was already known in this region in Babylonian astronomy, while Greek astronomy also came to use the Balance alongside the older Claws tradition. The Scales identity became firmly established in the Roman tradition, and it was Libra—the Balance—rather than the Scorpion’s Claws that ultimately endured as the constellation we recognize today.
The modern sky therefore preserves traces of both traditions: the constellation is Libra, the Scales, but its two brightest stars still carry the names of the Scorpion’s claws.
Four Stars Give Libra Its Shape
Four stars provide the main framework for Libra’s traditional figure. Zubeneschamali and Zubenelgenubi are the brightest, while two fainter stars help complete the pattern:
- Zubeneschamali (Beta Librae) — the brightest member of Libra, a hot blue-white main-sequence star about 185 light-years away.
- Zubenelgenubi (Alpha Librae) — the constellation’s second-brightest star, about 75 light-years away and an easy double-star target through binoculars.
- Zubenelhakrabi (Gamma Librae) — a fainter orange giant that helps define the northern part of Libra’s main figure.
- Brachium (Sigma Librae) — a red giant marking another point in the traditional Scales pattern.
The Star That Seemed Older Than the Universe
One of Libra’s most remarkable stars isn’t part of the familiar Scales pattern at all. HD 140283, about 190 light-years away, is nicknamed the Methuselah Star after the biblical figure famous for his longevity—and for good reason. Astronomers had tracked it for over a century due to its unusually fast motion across the sky, but it was the star’s chemistry that made it famous: HD 140283 is remarkably “metal-poor,” meaning it contains very little of the heavier elements—in astronomy, essentially anything beyond hydrogen and helium—that later generations of stars produced and scattered into space. Such a low abundance of heavy elements indicates that HD 140283 formed very early in cosmic history.
Early estimates put the star’s age at an impossible 16 billion years—older than the universe itself. In 2013, refined Hubble measurements brought that down to about 14.5 billion years, still older than the 13.8-billion-year-old universe, though the estimate’s own uncertainty—roughly 800 million years—meant the numbers weren’t strictly incompatible, just startling. A 2014 analysis refined the estimate to 14.27 billion years, while later studies produced younger values; a 2021 analysis put its age at around 12 billion years, removing the apparent conflict with the age of the universe.
HD 140283 was never really a star older than the universe. The apparent contradiction gradually faded as better measurements and improved stellar models refined its estimated age. What remains clear throughout these revisions is that this is an exceptionally ancient star, formed when the universe itself was still young.
Some of Libra’s Oldest Stars Shine Blue
Libra contains no Messier objects and relatively few prominent deep-sky targets, but NGC 5897 is a notable exception. This globular cluster lies about 40,000 light-years from Earth and is thought to be roughly 12 billion years old or more, making it a surviving relic from the early history of the Milky Way.
NGC 5897 is an ancient community of stars rather than a uniform swarm. Among its evolved red giants are many blue horizontal-branch stars. Their blue color might seem surprising in such an old population because blue stars are often associated with youth. But a star’s color primarily reflects its surface temperature, not simply its age. These stars have already passed through the red-giant stage and are now burning helium in their cores; their hotter surfaces make them appear blue.
NGC 5897 is also relatively loose and diffuse for a globular cluster, rather than being packed into an intensely concentrated ball of light. Through a telescope it appears as a broad, faint haze, while larger instruments under dark skies can begin to resolve some of its individual stars. Its appearance may be understated, but we’re looking at a community of stars whose history stretches back almost to the youth of the Milky Way.
You can explore more targets in our guide to deep-sky objects in Libra.
Virgo Holds Libra’s Scales of Justice
Libra is closely linked with neighboring Virgo in traditional depictions of the constellations. Virgo’s Maiden is sometimes shown holding the Scales represented by Libra, reflecting a traditional association between the two constellations and justice. In one classical tradition, Virgo was identified with Astraea, the goddess of justice, making the neighboring Scales a natural companion to the Maiden. This isn’t the origin of Libra—the Balance was known much earlier—but it helped create the familiar image of Virgo and the Scales side by side.
The name Libra has also survived far beyond astronomy. The Latin libra meant a balance or scales and gave its name to a Roman measure of weight. Its legacy remains in everyday use today: the abbreviation “lb” for pound comes from libra.
