Epoch J2000.0 Equinox J2000.0
|Right ascension||14h 50m 41.18097s|
|Declination||–15° 59′ 50.0482″|
|Apparent magnitude (V)||+5.153|
|Right ascension||14h 50m 52.71309s|
|Declination||–16° 02′ 30.3955″|
|Apparent magnitude (V)||+2.741|
|Spectral type||F3 V + kA2h + A5m + A4 IV-V|
|U−B color index||–0.002/+0.155|
|B−V color index||+0.394/+0.146|
|Radial velocity (Rv)||±0.4−24.7 km/s|
|Proper motion (μ)||RA: –136.27 mas/yr
Dec.: –59.04 mas/yr
|Parallax (π)||43.52 ± 0.43 mas|
|Distance||74.9 ± 0.7 ly
(23.0 ± 0.2 pc)
|Absolute magnitude (MV)||+3.29|
|Proper motion (μ)||RA: –105.68 mas/yr
Dec.: –68.40 mas/yr
|Parallax (π)||43.03 ± 0.19 mas|
|Distance||75.8 ± 0.3 ly
(23.2 ± 0.1 pc)
|Absolute magnitude (MV)||+0.88|
|Surface gravity (log g)||4.25 cgs|
|Metallicity [Fe/H]||–0.02 dex|
|Rotational velocity (v sin i)||5.95 km/s|
|Surface gravity (log g)||3.91 cgs|
α Librae, α Lib, alf Lib, Kiffa Australis, Lanx australis, Zubenelgenubi.
|α1 Lib: 8 Librae, BD–15 3965, FK5 1387, HD 130819, HIP 72603, HR 5530, SAO 158836.|
|α2 Lib: 9 Librae, BD–15 3966, FK5 548, HD 130841, HIP 72622, HR 5531, SAO 158840.|
Alpha Librae (α Lib, α Librae), or Zubenelgenubi, is the second brightest star in the constellation Libra (despite its Bayer designation as alpha). Alpha2 Librae is 0.33 degree from the ecliptic so it can be easily occulted by the Moon and (very rarely) by planets. The next occultation by a planet will be by Mercury on 10 November 2052.
Alpha Librae is the Bayer designation. It has the traditional name Zubenelgenubi //, also rendered Zuben Elgenubi. The name, from Arabic ّالزُبَانَى الجَنُوبِي al-zubānā al-janūbiyy, means "the southern claw" and was coined before Libra was recognized as a constellation distinct from Scorpius. The alternative name Kiffa Australis (Elkhiffa Australis) is a partial Latin translation of the Arabic al-kiffah al-janūbiyy "southern pan (of the scales)". Another name used in older astronomy texts, equivalent to "southern pan", was Lanx Australis.
Alpha Librae is about 77 light-years (24 parsecs) from the Sun. The two brightest components of Alpha Librae form a double star moving together through space as common proper motion companions. The brightest member, α2 Librae, is itself a spectroscopic binary system. The second member, α1 Librae, is separated from the primary system by around AU. It too is a spectroscopic binary with an orbital period of 5,870 days and an 5400 angular separation of 0.383 arcseconds; equal to about 10 AU. The system may have a fifth component, the star KU Librae at a separation of 2.6°, thus forming a hierarchical quintuple star system. KU Lib shares a similar motion through space to the Alpha Librae system, but is separated from the other stars by about a parsec. Still, it is sufficiently close to be gravitationally bound to the other members.
The two brightest members of Alpha Librae are separated in the sky by an angular distance of 231" (3'51"). The position angle of the companion is 314 degrees. The brighter of the two is a white star of spectral type A3, with an apparent brightness of 2.8. Its companion is a type F4 star of apparent brightness 5.2. They are probably members of the Castor Moving Group of stars that have a similar motion through space and share a common origin some 200 million years ago.
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- Caballero, J. A. (May 2010), "Reaching the boundary between stellar kinematic groups and very wide binaries. II. α Librae + KU Librae: a common proper motion system in Castor separated by 1.0 pc", Astronomy and Astrophysics, 514: A98, arXiv:, Bibcode:2010A&A...514A..98C, doi:10.1051/0004-6361/200913986
- "HD 130819 -- Star in Double System", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg
- "HD 130841 -- Variable Star", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2007-01-23
- Peuschel, Marco (2003). "Astronomische Ereignisse der besonderen Art". Retrieved July 10, 2005.
- Philippe La Hire, "Tabulae Astronomicae" (1727), see star table, page 13.
- Kaler, Jim (2004). "STARS: Zubenelgenubi". Retrieved July 10, 2005.
- Alpha Librae on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images