Alpha Librae

{{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

| component1 = α¹ Lib

| ra1 = {{RA|14|50|41.18097}}

| dec1 = {{DEC|-15|59|50.0482}}

| appmag_v1 = +5.153

| component2 = α² Lib

| ra2 = {{RA|14|50|52.71309}}

| dec2 = {{DEC|-16|02|30.3955}}

| appmag_v2 = +2.741

}}

{{Starbox character

| component = α¹ Lib

| class = F3 V

| b-v = +0.39

| u-b = −0.02

| variable =

}}

{{Starbox character|no_heading=y

| component = α² Lib

| class = kA2hA5mA4 IV-V

| b-v = +0.15{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1|date=1986|bibcode=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 }}

| u-b = +0.10

| variable =

}}

{{Starbox astrometry

| component1 = α¹ Lib

| radial_v = −23.47

| prop_mo_ra = −136.27

| prop_mo_dec = −59.04

| parallax = 43.52

| p_error = 0.43

| parallax_footnote =

| absmag_v = +3.35

| component2 = α² Lib

| radial_v2 =

| prop_mo_ra2 = −105.68

| prop_mo_dec2 = −68.40

| parallax2 = 43.03

| p_error2 = 0.19

| parallax_footnote2 =

| absmag_v2 =

}}

{{Starbox orbit

| reference =

| primary = α² Lib A

| name = α² Lib B

| period_unitless = 70.34 days

| eccentricity = 0.41

| axis_unitless = 0.51 au

| k2 = 43.1

}}

{{Starbox detail

| component1 = α¹ Lib A

| mass = {{val|1.36|0.02}}

| radius = {{solar radius calculator|type=logLT|0.55|6707|decimals=2}}0{{efn|name=radius}}

| luminosity = 3.55

| temperature = {{val|6707|56|fmt=commas}}

| metal_fe = {{val|-0.03}}

| gravity = 4.27

| rotational_velocity = 5.95

| age_gyr = {{val|1.01|0.24}}

| component2 = α¹ Lib B

| mass2 = 0.5–0.6

}}

{{Starbox detail|no_heading=y

| component1 = α² Lib A

| mass = 1.95

| radius = 2.21

| temperature = 8,200

| gravity = 3.91

| component2 = α² Lib B

| mass2 = 1.79

| radius2 = 1.92

| temperature2 = 7,930

}}

{{Starbox catalog

| names = Zubenelgenubi, Kiffa Australis, Lanx Australis, α Lib.

| component1 = α¹ Lib

| names1 = 8 Librae, BD−15 3965, FK5 1387, HD 130819, HIP 72603, HR 5530, SAO 158836.

| component2 = α² Lib

| names2 = 9 Librae, BD−15 3966, FK5 548, HD 130841, HIP 72622, HR 5531, SAO 158840.

}}

{{Starbox reference

|Simbad=alf+Lib|sn=α Lib

|Simbad2=alf01+Lib|sn2=α¹ Lib

|Simbad3=alf02+Lib|sn3=α² Lib

}}

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 {{IPAc-en|z|uː|ˌ|b|ɛ|n|ɛ|l|dʒ|ɪ|ˈ|n|uː|b|i}},{{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

}} though the International Astronomical Union now regards that name as only applying to α² Librae.{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}

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; the next occultation by a planet will be by Mercury on 10 November 2052.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. Both components are eclipsed (occulted) by the sun from about 7–9 November.[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 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 {{IPAc-en|,|z|u:|b|@n|E|l|dZ|@|'|n|u:|b|i}}, 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.[https://archive.org/stream/tabulaeastronom00suntgoog#page/n146/mode/2up Philippe La Hire, "Tabulae Astronomicae" (1727), see star table, page 13.]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{citation

| url=https://www.iau.org/science/scientific_bodies/working_groups/280/

| title=IAU Working Group on Star Names (WGSN)

| publisher=International Astronomical Union

| access-date=22 May 2016 | postscript=. }} 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.

In Chinese, {{lang|zh|氐宿}} ({{lang|zh-Latn|Dī Xiù}}), meaning Root, refers to an asterism consisting of α² Librae, ι Librae, γ Librae and β Librae.{{in lang|zh}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}. Consequently, the Chinese name for α² Librae itself is {{lang|zh|氐宿一}} ({{lang|zh-Latn|Dī Xiù yī}}), "the First Star of Root".{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.

Properties

Alpha Librae is about {{Convert|77|ly|pc|abbr=off|lk=on}} 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.

= Alpha<sup>2</sup> 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.{{Cite journal |last1=Waisberg |first1=Idel |last2=Klein |first2=Ygal |last3=Katz |first3=Boaz |date=2023-08-23 |title=Hidden Companions to Intermediate-mass Stars. X. Solving for the Mass Ratio in the Spectroscopic Binary Zubenelgenubi = α ² Librae* |journal=Research Notes of the AAS |volume=7 |issue=8 |pages=180 |doi=10.3847/2515-5172/acf28f |bibcode=2023RNAAS...7..180W |issn=2515-5172|doi-access=free }}

= Alpha<sup>1</sup> Librae =

The second member, α¹ Librae, is separated from the primary system by around {{val|5400|ul=AU}}. 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, but has a substantially different metallicity, making it unlikely to be physically bound to the system.

Notes

{{Notelist|notes=

{{Efn|name=radius|1=Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K: $\sqrt{\biggl(\frac{5,772}{6,707}\biggr)^4 \cdot 10^{0.55}} = 1.40\ R_\odot.$ }}

}}

References

{{reflist|refs=

{{cite journal|bibcode=2015ApJ...809..107F|title=Multiplicity among F-type stars. II|journal=The Astrophysical Journal|volume=809|pages=107|last1=Fuhrmann|first1=K.|last2=Chini|first2=R.|year=2015|issue=1|doi=10.1088/0004-637X/809/1/107|s2cid=126218052 |doi-access=}}

{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}

{{citation | display-authors=1 | last1=Gray | first1=R. O. | last2=Corbally | first2=C. J. | last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T. | last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E. | last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R. | title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G |arxiv = astro-ph/0603770 | s2cid=119476992 }}

{{citation | last1=Holmberg | first1=J. | last2=Nordström | first2=B. | last3=Andersen | first3=J. | title=The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics | journal=Astronomy and Astrophysics | volume=501 | issue=3 | pages=941–947 |date=July 2009 | doi=10.1051/0004-6361/200811191 | bibcode=2009A&A...501..941H |arxiv = 0811.3982 | s2cid=118577511 }}

{{citation | display-authors=1 | last1=Gutierrez-Moreno | first1=Adelina | last2=Moreno | first2=H. | last3=Stock | first3=J. | last4=Torres | first4=C. | last5=Wroblewski | first5=H. | title=A System of photometric standards | journal=Publ. Dept. Astron. Univ. Chile | publisher=Publicaciones Universidad de Chile, Department de Astronomy | volume=1 | pages=1–17 | date=1966 | bibcode=1966PDAUC...1....1G }}

{{citation | last1=Caballero | first1=J. A. | title=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 | journal=Astronomy and Astrophysics | volume=514 | page=A98 |date=May 2010 | doi=10.1051/0004-6361/200913986 | bibcode=2010A&A...514A..98C | arxiv=1001.5432 | s2cid=118875432 }}

{{Citation |last=Luck |first=R. Earle |date=2018-03-01 |title=Abundances in the Local Region. III. Southern F, G, and K Dwarfs |bibcode=2018AJ....155..111L |journal=The Astronomical Journal |volume=155 |issue=3 |pages=111 |doi=10.3847/1538-3881/aaa9b5 |doi-access=free |issn=0004-6256}} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/AJ/155/111&ID=*%20alf01%20Lib Alpha1 Librae's database entry] at VizieR.

{{cite journal|bibcode=1988mcts.book.....H|title=Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0|journal=Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4|last1=Houk|first1=N.|last2=Smith-Moore|first2=M.|year=1988}}

{{cite journal|bibcode=2014MNRAS.437.2303F|title=On the bright A-type star Alpha Librae A|journal=Monthly Notices of the Royal Astronomical Society|volume=437|issue=3|pages=2303|last1=Fuhrmann|first1=K.|last2=Chini|first2=R.|last3=Barr|first3=A.|last4=Buda|first4=L.-S.|last5=Kaderhandt|first5=L.|last6=Pozo|first6=F.|last7=Ramolla|first7=M.|year=2014|doi=10.1093/mnras/stt2046|doi-access=free}}

{{cite journal

| title=Planetary occultations of bright stars.

| last1=Können | first1=G. P. | last2=Van Maanen | first2=J.

| journal=Journal of the British Astronomical Association

| volume=91 | pages=148–157 | date=April 1981

| bibcode=1981JBAA...91..148K }}

}}

External links

Kaler, Jim (2004). [https://web.archive.org/web/20050818161632/http://www.astro.uiuc.edu/~kaler/sow/zubenel.html "STARS: Zubenelgenubi"]. Retrieved July 10, 2005.
{{WikiSky}}

Librae, Alpha

Category:Binary stars

Category:Libra (constellation)

Category:A-type subgiants

Category:F-type main-sequence stars

Zubenelgenubi

Category:Castor Moving Group