Libra is a southern zodiacal constellation that represents the Weighing Scales. It lies between Virgo and Scorpius on the ecliptic. Hold your mouse cursor over the image to see constellation figures, boundaries, and star identifications. Alpha Librae, Zubenelgenubi, is a wide double star that can be easily found halfway between the bright stars Spica and Antares. The components are separated by 231 arcseconds, or almost 4 arcminutes. The brighter primary is a spectral-type A3 star that shines at magnitude 2.75. The secondary shines at magnitude 5.15 and is an F4V spectral type star. The pair is located 77 light-years distant. Beta Librae, Zubenelschamali, is actually the brightest star in the constellation at magnitude 2.61. It is a spectral-type B8V blue star that is located 160 light-years from Earth. Gamma Librae, Zubenelakrab, is a spectral-type K star that shines at magnitude 3.91 and is located 152 light-years away. Zubenelgenubi and Zubenelschamali now represent the two ends of the balance beam of the Weighing Scales. Gamma Librae and Sigma Librae represent the weighing pans of the scales. Zubenelgenubi, however, means the "Southern Claw" and Zubenelschamali means the "Northern Claw". Gamma Librae, Zubenelakrab, means the "Shears of the Scorpion". All are Arabic names for the claws of the scorpion, which were originally part of the constellation of Scorpius. The claws later became part of the constellation of Libra, probably sometime during the days of the Roman empire. The Sun is located in the constellation of Libra from October 31 to November 23. Libra does not contain any Messier objects or spectacular deep-sky objects, but because the ecliptic runs through it, the Sun, Moon, and planets often pass through it. Libra was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the 29th largest of today's 88 modern constellations, covering 538 square degrees of sky. North is to the top in the above image.
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