Alpha Librae: Encyclopedia - Alpha Librae

Alpha Librae

Alpha Librae (α Lib / α Librae) is the second brightest star in the constellation Libra (despite its Bayer designation as "alpha"). It also has the traditional name Zubenelgenubi.

Alpha Librae is located approximately 77 light years from the Sun. It is actually a visual binary consisting of two stars separated in the sky by an angular distance of 231" (3'51"). The brighter of the two is a white star of spectral type A3, with an apparent brightness of 2.8 and an absolute brightness of 1.1, designated alpha-2 Librae (α² Lib). Its companion is a type F4 star of apparent brightness 5.2 and absolute brightness 3.5, designated alpha-1 Librae (α¹ Lib).

Alpha Librae is close to the ecliptic so it can be easily occulted by the Moon and (very rarely) by planets. The next occultation by a planet will take place on 10 November 2052 with Mercury^[1].

The name, from Arabic الزبن الجنوبي (az-zuban al-janūbiyy), means "southern claw" and was coined before Libra was recognized as distinct from Scorpius. The alternate names Kiffa Australis and Elkhiffa Australis, partial Latin translations of Arabic al-kiffah al-janūbiyy, mean "southern pan (of the scales)".

Coordinates of the main star (equinox 2000.0)

• Right Ascension 14h50m52s
• Declination −15°50'0"

Coordinates of the companion (equinox 2000.0)

• Right Ascension 14h50m41s
• Declination −15°59'49"

The position angle of the companion is 314 degrees.

Adapted from the Wikipedia article "Alpha Librae", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki