Beta Librae
Beta Librae (β Lib, β Librae), or Zubeneschamali, is the brightest star in the zodiac constellation of Libra. The apparent visual magnitude of this star is 2.6. From parallax measurements, its distance can be estimated as 185 light-years (57 parsecs) from Earth.
Name
Beta Librae is the Bayer designation. It has the traditional name Zubeneschamali /ˌzuːbənˌɛʃəˈmeɪli/ and the Latin name Lanx Borealis meaning "the northern pan [of the scales]". The name Zubeneschamali is derived from the Arabic ّالزُبَانَى الشَمَالِي (al-zubānā al-šamāliyy) meaning "The Northern Claw". Less common renderings (or corruptions) are Zuben Eschamali, Zuben el Chamali, Zubenesch, Zubenelg; there is also Kiffa Borealis, from the Arabic al-kiffah aš-šamāliyy "the northern pan (of the scales)".
Properties
Based upon the features of its spectrum, Beta Librae has a stellar classification of B8 V, making it a B-type main sequence star. It is about 130 times more luminous than the Sun and has a surface temperature of 7004123000000000000♠12300 K, double that of the Sun. This high temperature produces light with a simple spectrum, making it ideal for examining the interstellar gas and dust between us and the star. Like many stars of its kind, it is spinning rapidly, over 100 times faster than the Sun with a projected rotational velocity of 250 km·s−1. The measured angular diameter of the primary star is 0.801 mas. At the estimated distance of this system, this yields a physical size of about 4.9 times the radius of the Sun. This type of massive, hydrogen-fusing star often appears blue-white, and is usually stated to be white or bluish by modern observers, but earlier observers often described Beta Librae as the only greenish star visible to the naked eye. There seems to be no generally accepted explanation for why some observers see it as green.
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