Editing Alpha Librae (section)

{{short description|Binary star in the constellation Libra}}
{{Starbox begin
 | name = α Librae
}}
{{Starbox image
 | image=
{{Location mark
|image=Libra constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=α Librae
|x=657|y=410
}}
|caption=Location of α Librae (circled)
}}
{{Starbox observe 2s
 | epoch       = [[J2000.0]]
 | constell    = [[Libra (constellation)|Libra]]
 | component1  = α<sup>1</sup> Lib
 | ra1         = {{RA|14|50|41.18097}}<ref name=aaa474_2_653/>
 | dec1        = {{DEC|-15|59|50.0482}}<ref name=aaa474_2_653/>
 | appmag_v1   = +5.153<ref name=sps1966/>
 | component2  = α<sup>2</sup> Lib
 | ra2         = {{RA|14|50|52.71309}}<ref name=aaa474_2_653/>
 | dec2        = {{DEC|-16|02|30.3955}}<ref name=aaa474_2_653/>
 | appmag_v2   = +2.741<ref name=sps1966/>
}}
{{Starbox character
 | component = α<sup>1</sup> Lib
 | class       = F3 V<ref name=mk/>
 | b-v         = +0.39<ref name=EgUBV/>
 | u-b         = −0.02<ref name=EgUBV/>
 | variable    = 
}}
{{Starbox character|no_heading=y
 | component =  α<sup>2</sup> Lib
 | class       = kA2hA5mA4 IV-V<ref name=apj132_1_161/>
 | b-v         = +0.15<ref name=EgUBV>{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1|date=1986|bibcode= 1986EgUBV........0M }}</ref>
 | u-b         = +0.10<ref name=EgUBV/>
 | variable    = 
}}
{{Starbox astrometry
 | component1  = α<sup>1</sup> Lib
 | radial_v    = −23.47<ref name=orbit/>
 | prop_mo_ra  = −136.27<ref name=aaa474_2_653/>
 | prop_mo_dec = −59.04<ref name=aaa474_2_653/>
 | parallax    = 43.52
 | p_error     = 0.43
 | parallax_footnote = <ref name=aaa474_2_653/>
 | absmag_v    = +3.35<ref name=aaa501_3_941/>
 | component2 = α<sup>2</sup> Lib
 | radial_v2 = 
 | prop_mo_ra2 = −105.68<ref name=aaa474_2_653/>
 | prop_mo_dec2 = −68.40<ref name=aaa474_2_653/>
 | parallax2 = 43.03
 | p_error2 = 0.19
 | parallax_footnote2 = <ref name=aaa474_2_653/>
 | absmag_v2 =
}}
{{Starbox orbit
| reference = <ref name=orbit/>
| primary = α<sup>2</sup> Lib A
| name = α<sup>2</sup> Lib B
| period_unitless = 70.34 days
| eccentricity = 0.41
| axis_unitless = 0.51 au
| k2 = 43.1
}}
{{Starbox detail
 | component1  = α<sup>1</sup> Lib A
 | mass        = {{val|1.36|0.02}}<ref name="luck"/>
 | radius      = {{solar radius calculator|type=logLT|0.55|6707|decimals=2}}0<ref name="luck"/>{{efn|name=radius}}
 | luminosity  = 3.55<ref name="luck"/>
 | temperature = {{val|6707|56|fmt=commas}}<ref name="luck"/>
 | metal_fe    = {{val|-0.03}}<ref name="luck"/>
 | gravity     = 4.27<ref name="luck"/>
 | rotational_velocity = 5.95<ref name="luck"/>
 | age_gyr     = {{val|1.01|0.24}}<ref name="luck"/>
 | component2  = α<sup>1</sup> Lib B
 | mass2 = 0.5–0.6<ref name=aaa514_A98/>
}}
{{Starbox detail|no_heading=y
 | component1 = α<sup>2</sup> Lib A
 | mass = 1.95<ref name=waisberg/>
 | radius = 2.21<ref name=waisberg/>
 | temperature = 8,200<ref name=waisberg/>
 | gravity = 3.91<ref name=apj132_1_161/>
 | component2 = α<sup>2</sup> Lib B
 | mass2 = 1.79<ref name=waisberg/>
 | radius2 = 1.92<ref name=waisberg/>
 | temperature2 = 7,930<ref name=waisberg/>
}}
{{Starbox catalog
 | names = Zubenelgenubi, Kiffa Australis, Lanx Australis, α Lib.
 | component1 = α<sup>1</sup> Lib
 | names1 = 8 Librae, [[Bonner Durchmusterung|BD]]−15&nbsp;3965, [[FK5]]&nbsp;1387, [[Henry Draper Catalogue|HD]]&nbsp;130819, [[Hipparcos catalogue|HIP]]&nbsp;72603, [[Bright Star Catalogue|HR]]&nbsp;5530, [[Smithsonian Astrophysical Observatory Star Catalogue|SAO]]&nbsp;158836.<ref name=SIMBAD1/>
 | component2 = α<sup>2</sup> Lib
 | names2 = 9 Librae, [[Bonner Durchmusterung|BD]]−15&nbsp;3966, [[FK5]]&nbsp;548, [[Henry Draper Catalogue|HD]]&nbsp;130841, [[Hipparcos catalogue|HIP]]&nbsp;72622, [[Bright Star Catalogue|HR]]&nbsp;5531, [[Smithsonian Astrophysical Observatory Star Catalogue|SAO]]&nbsp;158840.<ref name=SIMBAD2/>
}}
{{Starbox reference
|Simbad=alf+Lib|sn=α Lib
|Simbad2=alf01+Lib|sn2=α<sup>1</sup> Lib
|Simbad3=alf02+Lib|sn3=α<sup>2</sup> Lib
}}
{{Starbox end}}
'''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 (constellation)|Libra]]. The two components are designated '''α<sup>1</sup> Librae''' and '''α<sup>2</sup> Librae'''. The system bore the traditional name of '''Zubenelgenubi''' {{IPAc-en|z|uː|ˌ|b|ɛ|n|ɛ|l|dʒ|ɪ|ˈ|n|uː|b|i}},<ref name=Kunitzsch>{{cite book
  |last1=Kunitzsch |first1=Paul
  |last2=Smart |first2=Tim
  |date = 2006  |edition = 2nd rev.
  |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
  |publisher = Sky Pub |location = Cambridge, Massachusetts
  |isbn = 978-1-931559-44-7
}}</ref> though the [[International Astronomical Union]] now regards that name as only applying to α<sup>2</sup> Librae.<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref>

Alpha<sup>2</sup> Librae is 0.33 degrees north of the [[ecliptic]] so it can be [[occultation|occulted]] by the [[Moon]] and (very rarely) by [[planet]]s. It was occulted by [[Venus]] on October 25, 1947;<ref name=Koennen1981/> the next occultation by a planet will be by [[Mercury (planet)|Mercury]] on 10 November 2052.<ref name=occultation>Peuschel, Marco (2003). [http://www.marco-peuschel.de/planetensterne.html "Astronomische Ereignisse der besonderen Art"] {{webarchive|url=https://web.archive.org/web/20050316042622/http://www.marco-peuschel.de/planetensterne.html |date=2005-03-16 }}. Retrieved July 10, 2005.</ref>  Both components are eclipsed ([[occultation|occulted]]) by the sun from about 7–9 November.<ref>[http://in-the-sky.org/skymap.php?year=2019&month=November&day=9 In the Sky] Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present</ref> Thus the star can be viewed the whole night, crossing the sky, in early May.