Alpha Librae

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Template:Short description

α Librae
Template:Location mark
Location of α Librae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Libra
α1 Lib
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) +5.153[2]
α2 Lib
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) +2.741[2]
Characteristics
α1 Lib
Spectral type F3 V[3]
U−B Template:Engvar −0.02[4]
B−V Template:Engvar +0.39[4]
α2 Lib
Spectral type kA2hA5mA4 IV-V[5]
U−B Template:Engvar +0.10[4]
B−V Template:Engvar +0.15[4]
Astrometry
α1 Lib
Radial velocity (Rv)−23.47[6] km/s
Proper motion (μ) RA: −136.27[1] mas/yr
Dec.: −59.04[1] mas/yr
Parallax (π)43.52±0.43 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+3.35[7]
α2 Lib
Proper motion (μ) RA: −105.68[1] mas/yr
Dec.: −68.40[1] mas/yr
Parallax (π)43.03±0.19 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Orbit[6]
Primaryα2 Lib A
Companionα2 Lib B
Period (P)70.34 days
Semi-major axis (a)0.51 au
Eccentricity (e)0.41
Semi-amplitude (K2)
(secondary)		43.1 km/s
Details
α1 Lib A
MassTemplate:Val[8] Template:Solar mass
RadiusTemplate:Solar radius calculator0[8]Template:Efn Template:Solar radius
Luminosity3.55[8] Template:Solar luminosity
Surface gravity (log g)4.27[8] cgs
TemperatureTemplate:Val[8] K
Metallicity [Fe/H]Template:Val[8] dex
Rotational velocity (v sin i)5.95[8] km/s
AgeTemplate:Val[8] Gyr
α1 Lib B
Mass0.5–0.6[9] Template:Solar mass
Metallicity [Fe/H]{{{metal_fe2}}} dex
α2 Lib A
Mass1.95[10] Template:Solar mass
Radius2.21[10] Template:Solar radius
Surface gravity (log g)3.91[5] cgs
Temperature8,200[10] K
α2 Lib B
Mass1.79[10] Template:Solar mass
Radius1.92[10] Template:Solar radius
Temperature7,930[10] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Zubenelgenubi, Kiffa Australis, Lanx Australis, α Lib.
α1 Lib: 8 Librae, BD−15 3965, FK5 1387, HD 130819, HIP 72603, HR 5530, SAO 158836.[11]
α2 Lib: 9 Librae, BD−15 3966, FK5 548, HD 130841, HIP 72622, HR 5531, SAO 158840.[12]
Database references
SIMBADα Lib
α1 Lib
α2 Lib

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Alpha Librae (α Librae, abbreviated Alpha Lib, α Lib) is a double star and, despite its 'alpha' designation, it is the second-brightest star system (or star) in the constellation of Libra. The two components are designated α1 Librae and α2 Librae. The system bore the traditional name of Zubenelgenubi Template:IPAc-en,[13] though the International Astronomical Union now regards that name as only applying to α2 Librae.[14]

Alpha2 Librae is 0.33 degrees north of the ecliptic so it can be occulted by the Moon and (very rarely) by planets. It was occulted by Venus on October 25, 1947;[15] the next occultation by a planet will be by Mercury on 10 November 2052.[16] Both components are eclipsed (occulted) by the sun from about 7–9 November.[17] Thus the star can be viewed the whole night, crossing the sky, in early May.

Nomenclature

α Librae (Latinised to Alpha Librae) is the system's Bayer designation.

Zubenelgenubi Template:IPAc-en, also rendered Zuben Elgenubi, derives from the Arabic ّالزُبَانَى الجَنُوبِي al-zubānā al-janūbiyy "the southern claw", which 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-janubiyyah الكفة الجنوبية "southern pan [of the scales]". Another name used in older astronomy texts, equivalent to "southern pan", was Lanx Australis.[18]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[19] to catalogue and standardize proper names for stars. The WGSN approved the name Zubenelgenubi for α2 Librae on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[14]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Root, refers to an asterism consisting of α2 Librae, ι Librae, γ Librae and β Librae.[20] Consequently, the Chinese name for α2 Librae itself is Script error: No such module "Lang". (Script error: No such module "Lang".), "the First Star of Root".[21]

Properties

Alpha Librae is about Template:Convert from the Sun. The two brightest components of Alpha Librae form a double star moving together through space as common proper motion companions. They 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 magnitude 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.[9]

Alpha2 Librae

The brightest member, α2 Librae, is itself a spectroscopic binary system. The components have similar masses (mass ratio of 0.92) but the primary has a rotational velocity three times higher than its companion, which could be caused by them having significantly misaligned spin axes or if the primary is a merger product.[10]

Alpha1 Librae

The second member, α1 Librae, is separated from the primary system by around Template:Val. It too is a spectroscopic binary with an orbital period of 5,870 days and an angular separation of 0.383 arcseconds; equal to about 10 AU.

KU Librae

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. It is sufficiently close to be gravitationally bound to the other members,[9] but has a substantially different metallicity, making it unlikely to be physically bound to the system.[22]

See also

Notes

Template:Notelist

References

Template:Reflist

External links

Template:Sky

Template:Stars of Libra

  1. ↑ a b c d e f g h i j Cite error: Invalid <ref> tag; no text was provided for refs named aaa474_2_653
  2. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named sps1966
  3. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named mk
  4. ↑ a b c d Script error: No such module "Citation/CS1".
  5. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named apj132_1_161
  6. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named orbit
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa501_3_941
  8. ↑ a b c d e f g h Cite error: Invalid <ref> tag; no text was provided for refs named luck
  9. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named aaa514_A98
  10. ↑ a b c d e f g Script error: No such module "Citation/CS1".
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD1
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD2
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ a b Script error: No such module "citation/CS1".
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Koennen1981
  16. ↑ Peuschel, Marco (2003). "Astronomische Ereignisse der besonderen Art" Template:Webarchive. Retrieved July 10, 2005.
  17. ↑ In the Sky Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
  18. ↑ Philippe La Hire, "Tabulae Astronomicae" (1727), see star table, page 13.
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  21. ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.
  22. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named multiplicity
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