View source for Capella

{{short description|Brightest star in the constellation Auriga}}
{{Other uses}}
{{featured article}}
{{Starbox begin}}
{{Starbox image
 | image=
{{Location mark
|image=Auriga constellation map.svg|alt=|float=center|width=300
|label=|position=right
|mark=Red circle.svg|mark_width=15|mark_link=Capella
|x=592|y=276
}}
|caption=Location of Capella Aa, as the brightest star (circled)
}}
{{Starbox observe 3s
 | pronounce    = {{IPAc-en|k|ə|ˈ|p|ɛ|l|ə}}<ref name=webster/>
 | appmag_v1    = +0.08<ref name=hr/> {{nowrap|(+0.03{{snd}}+0.16<ref name=petit/>)}}
 | appmag_v2    = 10.16<ref name=eggen/>
 | appmag_v3    = 13.7<ref name=agrawal/>
 | component1   = A
 | component3   = L
 | constell     = [[Auriga]]
 | dec1         = {{DEC|+45|59|52.7693}}<ref name="vanLeeuwen2007"/><ref group=note name=cg/>
 | dec2         = {{DEC|+45|50|22.97}}<ref name=ppm/>
 | component2   = H
 | dec3         = {{DEC|+45|50|19.84}}<ref name=2mass/>
 | epoch        = [[J2000.0]]
 | ra1          = {{RA|05|16|41.35871}}<ref name="vanLeeuwen2007"/><ref group=note name=cg>Pertains to the center of mass of the Capella Aa/Ab binary system.  See ''[https://www.cosmos.esa.int/documents/532822/552851/vol1_all.pdf Volume 1, The Hipparcos and Tycho Catalogues] {{Webarchive|url=https://web.archive.org/web/20180901145739/https://www.cosmos.esa.int/documents/532822/552851/vol1_all.pdf |date=2018-09-01 }}'', European Space Agency, 1997, §2.3.4, and the [http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%2024608 entry] {{Webarchive|url=https://web.archive.org/web/20160303185747/http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%2024608 |date=2016-03-03 }} in the Hipparcos catalogue ([[Centre de Données astronomiques de Strasbourg|CDS]] ID [http://vizier.u-strasbg.fr/viz-bin/Cat?I/239 I/239] {{Webarchive|url=https://web.archive.org/web/20160303181308/http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I%2F239%2Fh_dm_com&recno=1972 |date=2016-03-03 }}.)</ref>
 | ra2          = {{RA|05|17|23.728}}<ref name=ppm/>
 | ra3          = {{RA|05|17|23.943}}<ref name=2mass/>
 | equinox      = [[J2000.0]] ([[International Celestial Reference System|ICRS]])
}}
{{Starbox character
 | component    = A
 | class        = G3III:<ref name=perkins/>
 | r-i          = +0.44<ref name=hr/>
 | v-r          = −0.3<ref name=hr/>
 | b-v          = +0.80<ref name=hr/>
 | u-b          = +0.44<ref name=hr/>
 | variable     = [[RS Canum Venaticorum variable|RS CVn]]<ref name=audard/> (suspected<ref name=gcvs/>)
}}
{{Starbox character
 | no_heading   = yes
 | component    = Aa
 | type         = [[Red clump]]<ref name=torres15/>
 | class        = G8III<ref name=torres15/>
}}
{{Starbox character
 | no_heading   = yes
 | component    = Ab
 | type         = [[Subgiant#Subgiant branch|Subgiant]]<ref name=torres15/>
 | class        = G0III<ref name=torres15/>
}}
{{Starbox character
 | component    = H
 | type         = [[Main sequence]] ([[red dwarf]])<ref name=stauffer/>
 | class        = M2.5 V<ref name=joy/>
 | r-i          = 0.91<ref name=stauffer/>
 | b-v          = 1.50<ref name=stauffer/>
 | u-b          = 1.24<ref name=gliese/>
 | no_heading   = yes
}}
{{Starbox character
 | b-v          =
 | class        = M4:<ref name=bidelman/>
 | component    = L
 | no_heading   = yes
 | type         = [[Main sequence]] ([[red dwarf]])
}}
{{Starbox astrometry
 | radial_v     = +29.9387{{±|0.0032}}<ref name=torres15/>
 | prop_mo_ra   = 75.52<ref name="vanLeeuwen2007"/>
 | prop_mo_dec  = −427.11<ref name="vanLeeuwen2007"/>
 | parallax     = 76.20
 | p_error      = 0.46
 | parallax_footnote = <ref name="vanLeeuwen2007"/>
 | dist_ly      = 42.919{{±|0.049}}
 | dist_pc      = 13.159{{±|0.015}}<ref name=torres15/>
 | component1   = A
}}
{{Starbox astrometry
 | no_heading   = yes
 | component1   = Aa
 | absmag_v     = +0.296<ref name=torres15/>
 | component2   = Ab
 | absmag_v2    = +0.167<ref name=torres15/>
}}
{{Starbox astrometry
 | no_heading   = y
 | component1   = HL
 | radial_v2    = 31.63{{±|0.14}}<ref name=torres15/>
}}
{{Starbox astrometry
 | absmag_v     = 9.53<ref name=lowmass/>
 | absmag_v2    = 13.1<ref name=Johnson1983/>
 | component1   = H
 | component2   = L
 | no_heading   = yes
 | p_error      = 0.0188
 | p_error2     = 0.0534
 | parallax     = 74.9521
 | parallax2    = 75.1838
 | parallax_footnote  = <ref name="Gaia3h"/>
 | parallax_footnote2 = <ref name="Gaia3l"/>
 | prop_mo_dec  = −428.91<ref name=gaiadr2h/>
 | prop_mo_dec2 = −417.5<ref name=gaiadr2l/>
 | prop_mo_ra   = 88.57<ref name=gaiadr2h/>
 | prop_mo_ra2  = 54.1<ref name=gaiadr2l/>
}}
{{Starbox orbit
 | reference=<ref name=torres15/>
 | name         = Ab
 | primary      = Aa
 | period_unitless = {{val|104.02128|0.00016|u=days|fmt=commas}}
 | axis         = {{val|0.056442|0.000023|fmt=commas}}
 | axis_unitless= {{val|0.74272|0.00069|ul=AU|fmt=commas}}
 | eccentricity = {{val|0.00089|0.00011|fmt=commas}}
 | inclination  = {{val|137.156|0.046}}
 | node         = {{val|40.522|0.039}}
 | periastron   = {{val|2448147.6|2.6|ul=JD|fmt=commas}}
 | periarg_primary = {{val|342.6|9.0|ul=JD}}
 | k1           = {{val|25.9611|0.0044}}
 | k2           = {{val|26.860|0.0017}}
}}
{{Starbox orbit
 | axis         = 3.5
 | name         = L
 | primary      = H
 | axis_unitless= {{val|40|ul=AU}}<ref name=mult/>
 | eccentricity = 0.75
 | inclination  = 52
 | node         = 288
 | periarg      = 88
 | periastron   = 2,220
 | period       = 300
 | reference    = <ref name=torres15/>
}}
{{Starbox detail
 | source       = <ref name=torres15/>
 | no_heading   = 
 | component1   = Aa
 | mass         = 2.5687{{±|0.0074}}
 | radius       = 11.98{{±|0.57}}
 | luminosity_bolometric = 78.7{{±|4.2}}
 | temperature  = 4,970{{±|50}}
 | rotation     = 104{{±|3}} days
 | rotational_velocity = 4.1{{±|0.4}}
 | metal_fe     = −0.04{{±|0.06}}
 | gravity      = 2.691{{±|0.041}}
 | age_myr      = 590–650
 | component2   = Ab
 | mass2        = 2.4828{{±|0.0067}}
 | radius2      = 8.83{{±|0.33}}
 | luminosity_bolometric2 = 72.7{{±|3.6}}
 | temperature2 = 5,730{{±|60}}
 | rotation2    = 8.5{{±|0.2}} days
 | rotational_velocity2 = 35.0{{±|0.5}}
 | metal_fe2    = −0.04{{±|0.06}}
 | gravity2     = 2.941{{±|0.032}}
 | age_myr2     = 590–650
}}
{{Starbox detail
 | component1   = H
 | component2   = L
 | gravity      = 4.75{{±|0.05}}
 | luminosity_bolometric = 0.05<ref name=lowmass/>
 | mass         = 0.57<ref name=torres15/><ref name=mult/>
 | mass2        = 0.53<ref name=torres15/>
 | metal_fe     = +0.1<ref name=lowmass/>
 | radius       = 0.54{{±|0.03}}<ref name=lowmass/>
 | temperature  = 3,700{{±|150}}<ref name=lowmass/>
 | no_heading   = yes
}}
{{Starbox catalog
 | names1  = {{odlist | GJ=194 }}
 | component1 = A
 | component2 = HL
 | names2  = {{odlist | GJ=195 }}<ref name=gliese/>
 | names   = {{odlist | name=Alhajoth | name2=Hokulei | B=α Aurigae | F=13 Aurigae | ADS=3841 | BD=+45 1077 | CCDM=J05168+4559 | FK5=193 | GC=6427 | HD=34029 | HIP=24608 | HR=1708 | IDS=05093+4554 | LTT=11619 | NLTT=14766 | PPM=47925 | SAO=40186 | WDS=05167+4600 }}<ref name=sb0/><ref name=hr/>{{sfn|Brosch|2008|p=46}}<ref name=wds/><ref name=gliese/>
 | component3 = H
 | names3  = {{odlist | G=96-29 | LTT=11622 | NLTT=14788 | PPM=47938 | 2MASS=J05172386+4550229 }}<ref name=sb1/>
 | component4 = L
 | names4  = {{odlist | VVO=238 | 2MASS=J05172394+4550198 }}<ref name=sb2/>
}}
{{Starbox reference
 | Simbad  = alf+aur
 | Simbad2 = CCDM+J05168%2B4559H
 | Simbad3 = CCDM+J05168%2B4559L
 | sn      = Capella
 | sn3     = Capella L
 | sn2     = Capella H
}}
{{Starbox end}}

'''Capella''' is the brightest [[star]] in the northern [[constellation]] of [[Auriga]]. It has the [[Bayer designation]] '''α Aurigae''', which is [[Latinisation of names|Latinised]] to '''Alpha Aurigae''' and abbreviated '''Alpha Aur''' or '''α Aur'''. Capella is the [[list of brightest stars|sixth-brightest]] star in the [[night sky]], and the third-brightest in the [[northern celestial hemisphere]] after [[Arcturus]] and [[Vega]]. A prominent object in the northern sky, it is [[Circumpolar star|circumpolar]] to observers north of [[44°N]]. Its name meaning "little goat" in [[Latin]], Capella depicted the goat [[Amalthea (mythology)|Amalthea]] that suckled [[Zeus]] in classical mythology. Capella is relatively close, at {{convert|42.9|ly|pc|lk=on|abbr=off}}. It is one of the brightest [[X-ray]] sources in the sky, thought to come primarily from the [[stellar corona|corona]] of Capella Aa.

Although it appears to be a single star to the naked eye, Capella is actually a quadruple [[star system]] organized in two [[binary star|binary pairs]], made up of the stars Capella Aa, Capella Ab, Capella H and Capella L. The primary pair, Capella Aa and Capella Ab, are two bright-yellow [[giant star]]s, both of which are around 2.5 times as massive [[Solar mass|as the Sun]]. The secondary pair, Capella H and Capella L, are around 10,000 [[astronomical unit]]s (AU)<ref name="au" group="note">the distance between the Earth and the Sun is one astronomical unit</ref> from the first and are two faint, small and relatively cool [[red dwarf]]s.

Capella Aa and Capella Ab have exhausted their core [[hydrogen]], and cooled and expanded, moving off the [[main sequence]]. They are in a very tight circular orbit about 0.74 AU apart, and orbit each other every 104 days. Capella Aa is the cooler and more luminous of the two with [[spectral class]] G8III; it is 78.7{{±|4.2}} times the [[Sun's luminosity]] and 11.98{{±|0.57}} times [[Solar radius|its radius]]. An aging [[red clump]] star, it is fusing [[helium]] to [[carbon]] and [[oxygen]] in its core. Capella Ab is slightly smaller and hotter and of spectral class G0III; it is 72.7{{±|3.6}} times as luminous as the Sun and 8.83{{±|0.33}} times its radius. It is in the [[Hertzsprung gap]], corresponding to a brief [[subgiant]] evolutionary phase as it expands and cools to become a [[red giant]]. Several other stars in the same visual field have been catalogued as companions but are physically unrelated.

==Nomenclature==
[[File:AurigaCC.jpg|thumb|left|Capella is the brightest star in the constellation of Auriga (upper left).]]
''α Aurigae'' ([[Latinisation of names|Latinised]] to ''Alpha Aurigae'') is the star system's [[Bayer designation]]. It also has the [[Flamsteed designation]] 13 Aurigae. It is listed in several multiple star catalogues as [[Aitken Double Star Catalogue|ADS]] 3841, [[Catalog of Components of Double and Multiple Stars|CCDM]] J05168+4559, and [[Washington Double Star Catalog|WDS]] J05167+4600. As a relatively nearby star system, Capella is listed in the [[Gliese-Jahreiss Catalogue]] with designations GJ 194 for the bright pair of giants and GJ 195 for the faint pair of red dwarfs.

The traditional name ''Capella'' is [[Latin language|Latin]] for ''(small) female goat''; the alternative name ''Capra'' was more commonly used in classical times.<ref name="Kunitzsch">{{cite book |last1=Kunitzsch|first1=Paul |last2=Smart|first2= Tim |year = 2006 |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations |edition = 2nd rev. |publisher = [[Sky & Telescope|Sky Pub]]|isbn = 978-1-931559-44-7 |page = 19}}</ref> It is the translation of the Greek star name Aἴξ (aix) meaning "the Goat". As the sound of the Greek term for the goat (aἴξ) is similar to the sound of the name for the Aegaean Sea, this star has been used for weather rules and determining the seasonal wind direction.<ref>{{Cite book |last=Hoffmann |first=Susanne M. |title=Wie der Löwe an den Himmel kam Auf den Spuren der Sternbilder |date=2021 |publisher=Kosmos Verlag |isbn=978-3-440-17251-3 |edition=1. Auflage |location=Stuttgart |oclc=1243068585}}</ref> In 2016, the [[International Astronomical Union]] organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web|date=2016|author1=Mamajek, Eric|author2=García, Beatriz|author3=Hamacher, Duane|author4=Montmerle, Thierry|author5=Pasachoff, Jay|author6=Ridpath, Ian|author7=Sun, Xiaochun|author8=van Gent, Robert|url=https://www.iau.org/science/scientific_bodies/working_groups/280/|title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016|archive-date=10 June 2016|archive-url=https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/|url-status=live}}</ref> to catalogue and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1">{{cite web|url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf|title=Bulletin of the IAU Working Group on Star Names, No. 1|author1=Mamajek, Eric|author2=García, Beatriz|author3=Hamacher, Duane|author4=Montmerle, Thierry|author5=Pasachoff, Jay|author6=Ridpath, Ian|author7=Sun, Xiaochun|author8=van Gent, Robert|access-date=28 July 2016|archive-date=17 April 2018|archive-url=https://web.archive.org/web/20180417140227/http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf|url-status=live}}</ref> included a table of the first two batches of names approved by the WGSN; which included ''Capella'' for this star. It is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN">{{cite web|url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt|title=IAU Catalog of Star Names|author1=Mamajek, Eric|author2=García, Beatriz|author3=Hamacher, Duane|author4=Montmerle, Thierry|author5=Pasachoff, Jay|author6=Ridpath, Ian|author7=Sun, Xiaochun|author8=van Gent, Robert|date=July 2016|access-date=28 July 2016|archive-date=7 July 2018|archive-url=https://web.archive.org/web/20180707180747/http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt|url-status=live}}</ref> The catalogue of star names lists ''Capella'' as applying to the star α Aurigae Aa.<ref>{{Cite web |url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt |title=IAU Catalog of Star Names (IAU-CSN) |via=www.pas.rochester.edu |access-date=2016-08-14 |url-status=live |archive-date=2018-07-07 |archive-url=https://web.archive.org/web/20180707180747/http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt}}</ref>

==Observational history==
Capella was the brightest star in the night sky from 210,000 years ago to 160,000 years ago, at about −1.8 in [[apparent magnitude]]. At −1.1, [[Aldebaran]] was brightest before this period; it and Capella were situated rather close to each other in the sky and approximated boreal [[pole star]]s at the time.{{sfn|Schaaf |2008|p=155}}

[[File:Monte Albán archeological site, Oaxaca.jpg|thumb|left|Building J (foreground) at [[Monte Albán]]|alt= some ancient stone ruins of buildings in a sandy area]]
Capella is thought to be mentioned in an [[Akkadian language|Akkadian]] inscription dating to the 20th century BC.{{sfn|Schaaf |2008|p=152}} Its goat-associated symbolism dates back to [[Mesopotamia]] as a constellation called "GAM", "Gamlum" or "MUL.GAM" in the 7th-century BC document [[MUL.APIN]]. GAM represented a scimitar or crook and may have represented the star alone or the constellation of Auriga as a whole. Later, [[Bedouin]] astronomers created constellations that were groups of animals, where each star represented one animal. The stars of Auriga comprised a herd of goats, an association also present in Greek mythology.<ref name="rogers1998">{{cite journal | first=John H. | last=Rogers | date=1998 | title=Origins of the Ancient Constellations: I. The Mesopotamian traditions | journal=Journal of the British Astronomical Association | volume=108 |issue=1 | pages=9–28 | bibcode=1998JBAA..108....9R }}</ref> It is sometimes called the ''Shepherd's Star'' in English literature.{{sfn|Allen|2013|p=88}} Capella was seen as a portent of rain in classical times.{{sfn|Allen|2013|p=86}}

Building J of the [[pre-Columbian]] site [[Monte Albán]] in [[Oaxaca]] state in [[Mexico]] was built around 275 BC, at a different orientation to other structures in the complex. Its steps are aligned perpendicular to the rising of Capella at that time, so that a person looking out a doorway on the building would have faced it directly. Capella is significant as its [[heliacal rising]] took place within a day of the Sun passing directly overhead over Monte Albán.<ref>{{cite journal|date=1972|title=Mound J, Monte Albán: Possible Astronomical Orientation|journal=American Antiquity|volume=37|issue=4|pages=528–31 | doi=10.2307/278959|jstor=278959|author-link=Anthony Aveni|last1=Aveni |first1=Anthony F.|last2=Linsley|first2=Robert M.|s2cid=162239618 }}</ref>

===Multiple status===
Professor [[William Wallace Campbell]] of the [[Lick Observatory]] announced that Capella was binary in 1899, based on [[spectroscopic]] observations—he noted on photographic plates taken from August 1896 to February 1897 that a second [[stellar spectrum|spectrum]] appeared superimposed over the first, and that there was a [[Doppler effect|doppler shift]] to [[Blueshift|violet]] in September and October and to [[Redshift|red]] in November and February—showing that the components were moving toward and away from the Earth (and hence orbiting each other).<ref>{{cite journal|title=The Spectroscopic Binary Capella |author=Campbell, William Wallace |author-link=William Wallace Campbell | journal=Astrophysical Journal |volume=10 |date=October 1899 |page= 177|doi=10.1086/140625 |bibcode=1899ApJ....10..177C}}</ref><ref>{{cite journal|title=Variable Velocities of Stars in the Line of Sight | author= Newall, Hugh Frank |author-link=Hugh Newall | journal=The Observatory|volume=22|date=December 1899 |pages=436–37| bibcode=1899Obs....22..436N}}</ref> Almost simultaneously, British astronomer [[Hugh Newall]] had observed its composite spectrum with a four prism spectroscope attached to a {{convert|25|in|cm|adj=on}} [[Newall Telescope|telescope]] at Cambridge in July 1899, concluding that it was a [[binary star]] system.<ref>{{cite journal | title=The Binary System of Capella | author=Newall, Hugh Frank | journal=Monthly Notices of the Royal Astronomical Society | volume=60 | issue=6 | date=March 1900 | pages=418–20 | bibcode=1900MNRAS..60..418N | doi=10.1093/mnras/60.6.418 | url=https://zenodo.org/record/1431857 | doi-access=free | access-date=2019-08-27 | archive-date=2020-05-29 | archive-url=https://web.archive.org/web/20200529021037/https://zenodo.org/record/1431857 | url-status=live }}</ref>

Many observers tried to discern the component stars without success.<ref name="torres2009">{{cite journal|author=Torres, Guillermo|author2=Claret, Antonio|author3=Young, Patrick A.|date=2009|title=Binary Orbit, Physical Properties, and Evolutionary State of Capella (α Aurigae).|journal=The Astrophysical Journal|volume=700|issue=2|pages=1349–81|bibcode=2009ApJ...700.1349T|arxiv=0906.0977|doi=10.1088/0004-637X/700/2/1349|s2cid=16052567|url=https://digital.csic.es/bitstream/10261/24904/1/0004-637X_700_2_1349%20apj.pdf|access-date=2018-11-04|archive-date=2017-08-13|archive-url=https://web.archive.org/web/20170813072323/http://digital.csic.es/bitstream/10261/24904/1/0004-637X_700_2_1349%20apj.pdf|url-status=live}}</ref> Known as "The Interferometrist's Friend", it was first resolved [[Interferometry|interferometrically]] in 1919 by John Anderson and Francis Pease at [[Mount Wilson Observatory]], who published an orbit in 1920 based on their observations.<ref>{{cite journal |author=Mason, B. |pages=88–96 [94] |title=Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, Proceedings of the 240th Symposium of the International Astronomical Union, Held in Prague, Czech Republic: Classical Observations of Visual Binary and Multiple Stars |journal=Proceedings of the International Astronomical Union |volume=2 |date=August 22–25, 2006 |editor= William I. Hartkopf |editor2= Edward F. Guinan |editor3= Petr Harmanec|isbn=978-0-521-86348-3| doi=10.1017/S1743921307003857|s2cid=120643829 |doi-access=free }}</ref><ref>{{cite journal| title=Application of Michelson's Interferometer Method to the Measurement of Close Double Stars |author= Anderson, John A.| journal=Astrophysical Journal |volume=51 |date=1920 |pages= 263–75 |doi=10.1086/142551 | bibcode=1920ApJ....51..263A|doi-access=free }}</ref> This was the first interferometric measurement of any object outside the [[Solar System]].<ref name=lr>{{cite web|url=http://www.lchr.org/a/36/il/page4.html|title=Modern Optical Interferometry|author=Tubbs, Bob|date=April 1997|access-date=19 April 2017|archive-url=https://web.archive.org/web/20170420143550/http://www.lchr.org/a/36/il/page4.html|archive-date=2017-04-20}}</ref> A high-precision orbit was published in 1994 based on observations by the [[Mark III Stellar Interferometer]], again at Mount Wilson Observatory.<ref name=hummel94>{{cite journal|doi=10.1086/116995|bibcode=1994AJ....107.1859H|title=Very high precision orbit of Capella by long baseline interferometry|journal=The Astronomical Journal|volume=107|page=1859|year=1994|last1=Hummel|first1=C. A.|last2=Armstrong|first2=J. T.|last3=Quirrenbach|first3=A.|last4=Buscher|first4=D. F.|last5=Mozurkewich|first5=D.|last6=Elias|first6=N. M. II|last7=Wilson|first7=R. E.}} See §1 for spectral types, Table 1 for orbit, Table 5 for stellar parameters, and §6.3 for the age of the system.</ref> Capella also became the first astronomical object to be imaged by a separate element optical interferometer when it was imaged by the [[Cambridge Optical Aperture Synthesis Telescope]] in September 1995.<ref>{{cite journal|author=Baldwin, J. E.|author2=Beckett, M. G.|author3=Boysen, R. C.|author4=Burns, D.|author5=Buscher, D. F.|author6=Cox, G. C.|author7=Haniff, C. A.|author8=Mackay, C. D.|author9=Nightingale, N. S.|author10=Rogers, J.|author11=Scheuer, P. A. G.|author12=Scott, T. R.|author13=Tuthill, P. G.|author14=Warner, P. J.|author15=Wilson, D. M. A.|author16=Wilson, R. W. |title=The first images from an optical aperture synthesis array: mapping of Capella with COAST at two epochs |journal=Astronomy and Astrophysics |volume=306 |date=1996 |pages=L13–L16 |bibcode=1996A&A...306L..13B}}.</ref>

In 1914, Finnish astronomer [[Ragnar Furuhjelm]] observed that the spectroscopic binary had a faint companion star, which, as its [[proper motion]] was similar to that of the spectroscopic binary, was probably physically bound to it.<ref name=furuhjelm>{{cite journal |language=de |title=Ein schwacher Begleiter zu Capella |author=Furuhjelm, Ragnar |author-link=Ragnar Furuhjelm |journal=Astronomische Nachrichten |volume=197 |issue=11 |id=4715 |date=April 1914 |pages=181–82 |bibcode=1914AN....197..181F |doi=10.1002/asna.19141971103 |url=https://zenodo.org/record/1424898 |access-date=2020-09-30 |archive-date=2020-11-05 |archive-url=https://web.archive.org/web/20201105131609/https://zenodo.org/record/1424898 |url-status=live }}</ref> In February 1936, Carl L. Stearns observed that this companion appeared to be double itself;<ref name=stearns>{{cite journal|title=Note on duplicity of Capella H |author= Stearns, Carl L. |journal=Astronomical Journal |volume=45 |issue=1048 |date=July 1936|page= 120 |doi=10.1086/105349|bibcode=1936AJ.....45..120S|doi-access=free }}.</ref> this was confirmed in September that year by [[Gerard Kuiper]]. This pair are designated Capella H and L.<ref name=kuiper>{{cite journal|title=Confirmation of the Duplicity of Capella H |author=Kuiper, Gerard P.|author-link=Gerard Kuiper|journal=Astrophysical Journal|volume=84|date=October 1936|page= 359|doi=10.1086/143788|bibcode=1936ApJ....84Q.359K}}</ref>

===X-ray source===
Two [[Aerobee|Aerobee-Hi]] rocket flights on September 20, 1962, and March 15, 1963, detected and confirmed an [[X-ray]] source in Auriga at [[Right ascension|RA]] {{RA|05|09}} [[Declination|Dec]] {{Dec|+45}}, identified as Capella.<ref name=Fisher62>{{cite journal |author=Fisher, Philip C. |author2=Meyerott, Arthur J. |title=Stellar X-Ray Emission |journal=Astrophysical Journal |date=1964 |volume=139 |issue=1 |pages=123–42 |bibcode=1964ApJ...139..123F |doi=10.1086/147742 }}</ref> A major milestone in [[stellar X-ray astronomy]] happened on April 5, 1974, with the detection of the strongest emission of X-rays up to that time<ref>Philip A. Charles and Frederick D. Seward, ''Exploring the X-Ray Universe'' (Cambridge University Press, 1995) p.7</ref> from Capella, measured at more than 10,000 times the x-ray luminosity of the Sun.<ref name=Catura>{{cite journal |author=Catura, R. C. |author2=Acton, L. W. |author3=Johnson, H. M. |title=Evidence for X-ray emission from Capella |journal=Astrophysical Journal |date=1975 |volume=196 |issue=pt.2 |pages=L47–49 |doi=10.1086/181741 |bibcode=1975ApJ...196L..47C|doi-access=free }}</ref> A rocket flight on that date briefly calibrated its attitude control system when a star sensor pointed the payload axis at Capella. During this period, X-rays in the range 0.2–1.6 keV were detected by an X-ray reflector system co-aligned with the star sensor.<ref name=Catura/>

The X-ray luminosity (''L''<sub>x</sub>) of {{val|p=~|e=24|u=W}} ({{val|e=31|u=erg/s}}) is four orders of magnitude above the Sun's X-ray luminosity.<ref name=Catura/> Capella's X-rays are thought to be primarily from the [[stellar corona|corona]] of the most massive star.<ref>{{cite journal |author=Ishibashi, Kazunori |author2=Dewey, Daniel |author3=Huenemoerder, David P. |author4=Testa, Paola |title=Chandra/HETGS Observations of the Capella System: The Primary as a Dominating X-Ray Source |journal=The Astrophysical Journal |volume=644 |issue=2 |date=2006 |pages= L117–20 |doi=10.1086/505702 | bibcode=2006ApJ...644L.117I|arxiv = astro-ph/0605383 |s2cid=119444967 }}</ref> Capella is [[ROSAT]] X-ray source 1RXS J051642.2+460001. The high temperature of Capella's corona as obtained from the first coronal X-ray spectrum of Capella using [[HEAO 1]] would require magnetic confinement, unless it is a free-flowing coronal wind.<ref name=Gudel>{{cite journal |author=Güdel, Manuel |title=X-ray astronomy of stellar coronae |journal=The Astronomy and Astrophysics Review|date=2004 |volume=12 |issue=2–3 |pages=71–237 |doi=10.1007/s00159-004-0023-2 |arxiv = astro-ph/0406661 |bibcode = 2004A&ARv..12...71G|s2cid=119509015 }}</ref>

==Observation==
[[File:Другое -авиационный пейзаж и жанр, Прочее - Россия -RP56882.jpg|thumb|left|upright=1.2|Annotated night sky image showing [[Auriga (constellation)|Auriga]] and the [[Pleiades]]—Capella is the brightest star, towards top left|alt=photograph of night sky above a dimly-lit horizon]]
With an average apparent magnitude of +0.08, Capella is the brightest object in the [[constellation]] [[Auriga (constellation)|Auriga]], the [[list of brightest stars|sixth-brightest]] star in the night sky, the third-brightest in the [[Northern celestial hemisphere|northern]] [[Celestial sphere|celestial hemisphere]] (after [[Arcturus]] and [[Vega]]), and the fourth-brightest visible to the naked eye from the latitude [[40°N]]. It appears to be a rich yellowish-white colour, although the yellow colour is more apparent during daylight observation with a telescope, due to the contrast against the blue sky.{{sfn|Schaaf |2008|p=146}}

Capella is closer to the north [[celestial pole]] than any other [[first-magnitude star]].{{sfn|Burnham|1978|p=261}}<ref name=polaris group=note>[[Polaris]] is only second magnitude.</ref> Its northern declination is such that it is actually invisible south of latitude [[44th parallel south|44°S]]—this includes southernmost [[New Zealand]], [[Argentina]] and [[Chile]] as well as the [[Falkland Islands]]. Conversely it is [[circumpolar star|circumpolar]] north of [[44°N]]: for the whole of the [[United Kingdom]] and [[Canada]] (except for part of [[Southern Ontario]]), most of [[Europe]], and the northernmost fringes of the [[contiguous United States]], the star never sets. Capella and Vega are on opposite sides of the pole, at about the same distance from it, such that an imaginary line between the two stars will nearly pass through [[Polaris]].<ref name=Arnold>{{cite book|last=Arnold|first=H. P.|title=The Photographic Atlas of the Stars|date=1999|publisher=IOP Publishing Ltd.|isbn=978-0-7503-0654-6|page=68|url=https://books.google.com/books?id=YjcvJUfnWBAC&pg=PA68|access-date=2017-03-27|archive-date=2017-03-28|archive-url=https://web.archive.org/web/20170328041234/https://books.google.com/books?id=YjcvJUfnWBAC&pg=PA68|url-status=live}}</ref> Visible halfway between [[Orion's Belt]] and Polaris, Capella is at its highest in the night sky at midnight in early December and is regarded as a prominent star of the northern winter sky.<ref>{{cite book|last=Ball|first=Robert|title=A Primer of Astronomy|publisher=Cambridge University Press|date=2014|orig-date=1900|pages=194–95|isbn=978-1-107-42743-3|url=https://books.google.com/books?id=W2E3BAAAQBAJ&pg=PA195|access-date=2020-05-27|archive-date=2020-07-25|archive-url=https://web.archive.org/web/20200725035608/https://books.google.com/books?id=W2E3BAAAQBAJ&pg=PA195|url-status=live}}</ref>

A few degrees to the southwest of Capella lie three stars, [[Epsilon Aurigae]], [[Zeta Aurigae]] and [[Eta Aurigae]], the latter two of which are known as "The Kids", or [[Auriga (constellation)#Eclipsing binary stars|Haedi]]. The four form a familiar pattern, or [[Asterism (astronomy)|asterism]], in the sky.{{sfn|Ridpath|Tirion|2001|pp=86–88}}

==Distance==
Based on an annual [[parallax]] shift of 76.20 [[milliarcseconds]] (with a margin of error of 0.46 milliarcseconds) as measured by the [[Hipparcos]] satellite, this system is estimated to be {{Convert|13.12|pc|ly|abbr=off|lk=on|order=flip}} from [[Earth]], with a margin of error of 0.3 light-year (0.09 parsec).<ref name="vanLeeuwen2007">{{cite journal | first=F. | last=van Leeuwen | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–64 | date=November 2007 | bibcode=2007A&A...474..653V| doi=10.1051/0004-6361:20078357 | arxiv=0708.1752| s2cid=18759600 }}</ref> An alternative method to determine the distance is via the [[Cosmic distance ladder#Parallax|orbital parallax]], which gives a distance of {{convert|13.159|pc|ly|abbr=off|order=flip}} with a margin of error of only 0.1%.<ref name=torres15/> Capella is estimated to have been a little closer to the [[Solar System]] in the past, passing within 29 light-years distant around 237,000 years ago.<ref name=aa575_A35>{{cite journal | last1=Bailer-Jones | first1=C. A. L. | title=Close encounters of the stellar kind | journal=Astronomy & Astrophysics | volume=575 | id=A35 | page=13 | date=2015 | doi=10.1051/0004-6361/201425221 | bibcode=2015A&A...575A..35B |arxiv = 1412.3648 | s2cid=59039482 }}</ref> At this range, it would have shone at apparent magnitude −0.82, comparable to [[Canopus]] today.<ref>{{cite journal |last=Tomkin |first=Jocelyn |date=April 1998 |title=Once and Future Celestial Kings |journal=Sky and Telescope |volume=95 |issue=4 |pages=59–63 |bibcode=1998S&T....95d..59T}} – based on computations from [[Hipparcos]] data. (The calculations exclude stars whose distance or [[proper motion]] is uncertain.) [https://web.archive.org/web/20190407144220/http://connection.ebscohost.com/c/articles/259434/once-future-celestial-kings] [https://www.thefreelibrary.com/Once+and+future+celestial+kings-a020468305] {{Webarchive|url=https://web.archive.org/web/20200528041716/https://www.thefreelibrary.com/Once+and+future+celestial+kings-a020468305|date=2020-05-28}}</ref>

In a 1960 paper, American astronomer [[Olin J. Eggen]] concluded that Capella was a member of the [[Hyades moving group]], a group of stars moving in the same direction as the [[Hyades cluster]], after analysing its [[proper motion]] and [[parallax]]. Members of the group are of a similar age, and those that are around 2.5 times as massive as the Sun have moved off the [[main sequence]] after exhausting their core hydrogen reserves and are expanding and cooling into [[red giant]]s.<ref name=hr/><ref name="eggen1960">{{cite journal|author=Eggen, Olin J.|author-link=Olin Eggen|date=1960|title=Stellar Groups, VII. The Structure of the Hyades Group|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=120|issue=6|pages=540–62|bibcode=1960MNRAS.120..540E|doi=10.1093/mnras/120.6.540|doi-access=free}}</ref>

==Stellar system==
[[File:Capella-Sun comparison.png|thumb|upright=1.2|Capella components compared with the Sun|alt= two large pale yellow circles and three small circles on black background. They denote the two giants, and Sun and two dwarfs of the Capella system.]]
There are several stars within a few [[arcminutes]] of Capella and some have been listed as companions in various multiple star catalogues. The [[Washington Double Star Catalog]] lists components A, B, C, D, E, F, G, H, I, L, M, N, O, P, Q, and R, with A being the [[naked-eye]] star. Most are only [[optical double|line-of-sight]] companions,{{sfn|Schaaf |2008|p=154}} but the close pair of [[red dwarf]]s H and L are at the same distance as the bright component A and moving through space along with it.<ref name=chl/> Capella A is itself a [[spectroscopic binary]] with components Aa and Ab, both [[giant star]]s. The pair of giants is separated from the pair of red dwarfs by 723[[arc second|"]].<ref name=torres15/>

American astronomer [[Robert Burnham Jr.]] described a scale model of the system where Capella A was represented by spheres 13 and 7 inches across, separated by ten feet. The red dwarfs were then each 0.7 inch across and they were separated by 420 feet. At this scale, the two pairs are 21 miles apart.{{sfn|Burnham|1978|p=264}}

===Capella A===
[[File:Trackcapella.svg|thumb|left|upright=1.2|alt=Hertzsprung Russell diagram showing Capella Aa and Ab|[[Hertzsprung–Russell diagram]] showing an evolutionary track for a star of approximately the mass of the two Capella giants. The current states of Capella Aa and Ab are marked.<ref name=torres15/>]]
Capella A consists of two yellow [[stellar evolution|evolved]] stars that have been calculated to orbit each other every 104.02128{{±|0.00016}} days, with a [[semimajor axis]] of 111.11{{±|0.10}} million km ({{val|0.74272|0.00069|u=AU}}), roughly the distance between [[Venus]] and the Sun. The pair is not an eclipsing binary—that is, as seen from Earth, neither star passes in front of the other. The orbit is known extremely accurately and can be used to derive an [[Dynamical parallax|orbital parallax]] with far better precision than the one measured directly. The stars are not near enough to each other for the [[Roche lobe]] of either star to have been filled and any significant mass transfer to have taken place, even during the [[red giant]] stage of the primary star.<ref name="torres15"/><!-- cites para -->

Modern convention designates the more luminous cooler star as component Aa and its spectral type has been usually measured between G2 and K0. The hotter secondary Ab has been given various spectral types of late (cooler) G or early (warmer) F. The [[MK spectral classification|MK spectral types]] of the two stars have been measured a number of times, and they are both consistently assigned a luminosity class of III indicating a [[giant star]].<ref name="mk">{{cite journal|bibcode=2014yCat....1.2023S|title=VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009–2016)|journal=VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014)|volume=1|pages=B/mk|author-link=Brian A. Skiff|last1=Skiff|first1=Brian A.|year=2014}}</ref> The composite spectrum appears to be dominated by the primary star due to its sharper [[absorption line]]s; the lines from the secondary are broadened and blurred by its rapid rotation.<ref name="torres2009"/> The composite spectral class is given as approximately G3III, but with a specific mention of features due to a cooler component.<ref name="perkins"/> The most recent specific published types are K0III and G1III,<ref name="strassmeier"/> although older values are still widely quoted such as G5IIIe + G0III from the [[Bright Star Catalogue]]<ref name="hr"/> or G8III + G0III by Eggen.<ref name="eggen1960"/> Where the context is clear, these two components have been referred to as A and B.<ref name="weber2011"/>

The individual [[apparent magnitude]]s of the two component stars cannot be directly measured, but their relative brightness has been measured at various wavelengths. They have very nearly equal brightness in the visible light spectrum, with the hotter secondary component generally being found to be a few tenths of a magnitude brighter.<ref name="torres15"/> A 2016 measurement gives the magnitude difference between the two stars at a wavelength of 700&nbsp;nm as 0.00{{±|0.1}}.<ref name="hutter">{{cite journal|bibcode=2016ApJS..227....4H|arxiv=1609.05254|title=Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F–K|journal=The Astrophysical Journal Supplement Series|volume=227|issue=1|page=4|last1=Hutter|first1=D. J.|last2=Zavala|first2=R. T.|last3=Tycner|first3=C.|last4=Benson|first4=J. A.|last5=Hummel|first5=C. A.|last6=Sanborn|first6=J.|last7=Franz|first7=O. G.|last8=Johnston|first8=K. J.|year=2016|doi=10.3847/0067-0049/227/1/4|s2cid=118803592 |doi-access=free }}</ref>

The physical properties of the two stars can be determined with high accuracy. The masses are derived directly from the orbital solution, with Aa being {{val|2.5687|0.0074|ul=solar mass}} and Ab being {{val|2.4828|0.0067|u=solar mass}}. Their angular radii have been directly measured; in combination with the very accurate distance, this gives {{val|11.98|0.57|ul=solar radius}} and {{val|8.83|0.33|u=solar radius}} for Aa and Ab, respectively. Their [[effective temperature|surface temperatures]] can be calculated by comparison of observed and synthetic spectra, direct measurement of their angular diameters and brightnesses, calibration against their observed [[colour index|colour indices]], and disentangling of high resolution spectra. Weighted averages of these four methods give {{val|fmt=commas|4,970|50|ul=K}} for Aa and {{val|fmt=commas|5,730|60|u=K}} for Ab. Their [[bolometric luminosity|bolometric luminosities]] are most accurately derived from their apparent magnitudes and [[bolometric correction]]s, but are confirmed by calculation from the temperatures and radii of the stars. Aa is 78.7{{±|4.2}} times as luminous as the Sun and Ab 72.7{{±|3.6}} times as luminous, so the star defined as the primary component is the more luminous when all wavelengths are considered but very slightly less bright at visual wavelengths.<ref name="torres15"/>

Estimated to be 590 to 650 million years old,<ref name=torres15/> the stars were probably at the hot end of [[spectral class A]] during their [[main sequence|main-sequence]] lifetime, similar to [[Vega]]. They have now exhausted their core hydrogen and evolved off the main sequence, their outer layers expanding and cooling.{{sfn|Schaaf |2008|pp=153–55}} Despite the giant luminosity class, the secondary component is very clearly within the [[Hertzsprung gap]] on the [[Hertzsprung–Russell diagram]], still expanding and cooling towards the [[red giant branch]], making it a [[subgiant]] in evolutionary terms. The more massive primary has already passed through this stage, when it reached a maximum radius of 36 to 38 times that of the Sun. It is now a [[red clump]] star which is fusing [[helium]] to [[carbon]] and [[oxygen]] in its core, a process that has not yet begun for the less massive star. Detailed analysis shows that it is nearing the end of this stage and starting to expand again which will lead it to the [[asymptotic giant branch]]. [[Isotope abundance]]s<ref group=note name=ia>The lithium abundance, C<sub>12</sub>/C<sub>13</sub> ratio and C/N ratio have all declined in Capella Aa but not in Capella Ab.</ref> and spin rates confirm this evolutionary difference between the two stars. Heavy element abundances are broadly comparable to those of the Sun and the overall [[metallicity]] is slightly less than the Sun's.<ref name=torres2009/>

The rotational period of each star can be measured by observing periodic variations in the [[doppler shift]]s of their spectral lines. The absolute rotational velocities of the two stars are known from their inclinations, rotation periods, and sizes, but the [[projected rotational velocity|projected equatorial rotational velocities]] measured using [[doppler broadening]] of spectral lines are a standard measure and these are generally quoted.<ref name=torres2009/> Capella Aa has a projected rotational velocity of {{val|4.1|0.4|u=km/s}}, taking 104{{±|3}} days to complete one rotation, while Capella Ab spins much more rapidly at {{val|35.0|0.5|u=km/s}}, completing a full rotation in only 8.5{{±|0.2}} days. [[Stellar rotation#Rotation braking|Rotational braking]] occurs in all stars when they expand into giants, and binary stars are also [[Tidal acceleration|tidally braked]]. Capella Aa has slowed until it is rotationally locked to the orbital period, although theory predicts that it should still be rotating more quickly from a starting point of a rapidly-spinning main sequence A star.<ref name=torres15/>

Capella has long been suspected to be slightly variable. Its amplitude of about 0.1 magnitudes means that it may at times be brighter or fainter than [[Rigel]], [[Betelgeuse]] and [[Vega]], which are also variable. The system has been classified as an [[RS Canum Venaticorum variable]],<ref name=audard>{{cite conference|bibcode=2002cosp...34E1599A|title=Investigations of stellar coronae with XMM-Newton|journal=34th COSPAR Scientific Assembly|volume=34|last1=Audard|first1=M|year=2002}}</ref> a class of binary stars with active [[chromosphere]]s that cause huge [[starspot]]s, but it is still only listed as a suspected variable in the [[General Catalogue of Variable Stars]].<ref name=gcvs/> Unusually for RS CVn systems, the hotter star, Capella Ab, has the more active atmosphere because it is located in the Hertzsprung gap—a stage where it is changing its angular momentum and deepening its [[convection zone]].<ref name="weber2011">{{cite journal|author=Weber, M.|author2=Strassmeier, K. G.|date=2011|title=The Spectroscopic Orbit of Capella Revisited|journal=Astronomy & Astrophysics|volume=531|pages=id.A89 (5 pp.) |bibcode=2011A&A...531A..89W|arxiv = 1104.0342 |doi = 10.1051/0004-6361/201116885 |s2cid=119184231}}</ref>

The active atmospheres and closeness of these stars means that they are among the brightest [[X-ray]] sources in the sky. However the X-ray emission is due to stable coronal structures and not eruptive flaring activity. Coronal loops larger than the Sun and with temperatures of several million kelvin are likely to be responsible for the majority of the X-rays.<ref name=argiroffi>{{cite journal|bibcode=2003A&A...404.1033A|title=On coronal structures and their variability in active stars: The case of Capella observed with Chandra/LETGS|journal=Astronomy and Astrophysics|volume=404|issue=3|page=1033|last1=Argiroffi|first1=C.|last2=Maggio|first2=A.|last3=Peres|first3=G.|year=2003|doi=10.1051/0004-6361:20030497|doi-access=free}}</ref>

===Capella HL===
The seventh companion published for Capella, component H, is physically associated with the bright primary star. It is a [[red dwarf]] separated from the pair of G-type giants by a distance of around {{Val|10000|fmt=commas|u=AU}}.<ref name=chl>
{{cite book
 |last=Ayres |first=Thomas R.
 |year=1984
 |title=Cool Stars, Stellar Systems, and the Sun |chapter=Capella HL
 |series=Lecture Notes in Physics
 |volume=193 |page=202
 |isbn=978-3-540-12907-3
 |doi=10.1007/3-540-12907-3_204 |bibcode=1984LNP...193..202A
}}
</ref> It has its own close companion, an even fainter red dwarf that was 1.8″&nbsp;away when it was discovered in 1935. It is component&nbsp;L in double star catalogues. In 2015 the separation had increased to 3.5″, which was sufficient to allow ''tentative'' orbital parameters to be derived, 80&nbsp;years after its discovery.<ref name=torres15/><ref name=heintz75>
{{cite journal
 |last=Heintz |first=W.D. |author-link=Wulff-Dieter Heintz
 |year=1975
 |title=Parallax and motions of the Capella system
 |journal=The Astrophysical Journal
 |volume=195 |page=411
 |doi=10.1086/153340 |bibcode=1975ApJ...195..411H
}}
</ref> The [[Gliese-Jahreiss Catalogue]] of nearby stars designates the binary system as GJ&nbsp;195. The two components are then referred to individually as GJ&nbsp;195&nbsp;A and B.<ref name=gliese/>

The two stars are reported to have a 3.5-visual-magnitude difference (2.3&nbsp;mag in the passband of the [[Gaia (spacecraft)|''Gaia'']] spacecraft) although the difference is much smaller at [[infrared]] wavelengths. This is unexpected and may indicate further unseen companions.<ref name=torres15/>

The mass of the stars can, in principle, be determined from the orbital motion, but uncertainties in the orbit have led to widely varying results. In 1975, an eccentric 388-year orbit gave masses of {{solar mass|0.65|link=y}} and {{solar mass|0.13}}.<ref name=heintz75/> A smaller near-circular orbit published in 2015 had a 300-year orbit, benefitting from mass constraints of {{solar mass|0.57}} and {{solar mass|0.53}}, respectively, for GJ&nbsp;195&nbsp;A and B, based on their infrared magnitudes.<ref name=torres15/>

===Visual companions===
Six visual companions to Capella were discovered before Capella&nbsp;H and are generally known only as Capella&nbsp;B through G. None are thought to be physically associated with Capella, although all appear closer in the sky than the HL&nbsp;pair.{{sfn|Burnham|1978|p=264}}

{{Componentbox begin
 |designation=[[Washington Double Star Catalog|WDS]]&nbsp;05167+4600
 |footnote=<ref name=wds>
  {{cite web
 |title=Entry 05167+4600
 |website=The Washington Double Star Catalog
 |publisher=[[United States Naval Observatory]]
 |access-date=24 December 2008
 |url=http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewframe1.html
 |archive-url=https://web.archive.org/web/20110816042149/http://ad.usno.navy.mil/wds/Webtextfiles/wdsnewframe1.html
 |archive-date=2011-08-16
 }}
</ref>
 |expanded = yes
 |centered = yes
}}
{{Componentbox component
 |letter = B
 |primary = A
 |appmag_v = 17.1
 |epoch = 1898
 |posang= 23
 |angdist= 46.6
 |ra = {{RA|05|16|42.7}}
 |dec = {{DEC|+46|00|55}}
 |simbad =
 |expanded = yes
}}
{{Componentbox component
 |letter = C
 |primary = A
 |appmag_v = 15.1
 |epoch = 1878
 |posang= 318
 |angdist= 78.2
 |ra = {{RA|05|16|35.9}}
 |dec = {{DEC|+46|01|12}}
 |simbad =
 |expanded = yes
}}
{{Componentbox component
 |letter = D
 |primary = A
 |appmag_v = 13.6
 |epoch = 1878
 |posang= 183
 |angdist= 126.2
 |ra = {{RA|05|16|40.1}}
 |dec = {{DEC|+45|58|07}}
 |simbad =
 |expanded = yes
}}
{{Componentbox component
 |letter = E
 |primary = A
 |appmag_v = 12.1
 |epoch = 1908
 |posang= 319
 |angdist= 154.1
 |ra = {{RA|05|16.5}}
 |dec = {{DEC|+46|02}}
 |simbad =
 |expanded = yes
}}
{{Componentbox component
 |letter = F
 |primary = A
 |appmag_v = 10.21
 |epoch = 1999
 |posang= 137
 |angdist= 112.0
 |ra = {{RA|05|16|48.748}}
 |dec = {{DEC|+45|58|30.84}}
 |simbad = CCDM+J05168%2B4559F
 |expanded = yes
}}
{{Componentbox component
 |letter = G
 |primary = A
 |appmag_v = 8.10
 |epoch = 2003
 |posang= 349
 |angdist= 522.4
 |ra = {{RA|05|16|31.852}}
 |dec = {{DEC|+46|08|27.42}}
 |simbad = CCDM+J05168%2B4559G
 |expanded = yes
}}
{{Componentbox end}}

Component&nbsp;F is also known as TYC&nbsp; 3358-3142-1. It is listed with a spectral type of K<ref name=agk3>
{{cite book
 |last1=Heckmann |first1=O. |author-link=Otto Heckmann
 |year=1975
 |title=AGK&nbsp;3. Star catalogue of positions and proper motions north of −2.5&nbsp;deg. declination
 |place=Hamburg-Bergedorf
 |publisher=Hamburger Sternwarte
 |bibcode=1975ascp.book.....H
}}
</ref> although it is included in a catalogue of OB stars as a distant luminous star.<ref name=ob>
{{cite journal
 |last1=Gontcharov |first1=G.A.
 |year=2012
 |title=Spatial distribution and kinematics of OB stars
 |journal=Astronomy Letters
 |volume=38 |issue=11 |pages=694–706
 |doi=10.1134/S1063773712110035 |arxiv=1606.09028
 |s2cid=119108982 |bibcode=2012AstL...38..694G
}}
</ref>

Component&nbsp;G is BD+45&nbsp;1076, with a spectral type of F0,<ref name=agk3/> at a distance of {{convert|123|pc|ly|abbr=off|order=flip|sigfig=3}}.<ref name=hoffman/> It is identified as a variable member of the [[Guide Star Catalogue]] from [[Chandra X-ray Observatory|Chandra]] observations although it is not known what type of variability.<ref name=chandra>{{cite journal |last1=Nichols |first1=Joy S. |last2=Henden |first2=Arne A. |last3=Huenemoerder |first3=David P. |last4=Lauer |first4=Jennifer L. |last5=Martin |first5=Eric |last6=Morgan |first6=Douglas L. |last7=Sundheim |first7=Beth A. |year=2010 |title=The Chandra Variable Guide Star Catalog |journal=The Astrophysical Journal Supplement |volume=188 |issue=2 |page=473 |doi=10.1088/0067-0049/188/2/473 |hdl=1721.1/95684 |bibcode=2010ApJS..188..473N|s2cid=954298 |hdl-access=free }}</ref> It is known to be an X-ray source with an active corona.<ref name=hoffman>{{cite journal |arxiv=1209.5101 |bibcode=2012ApJ...759..145H |title=Constraints on the Ubiquity of Coronal X-Ray Cycles |journal=The Astrophysical Journal |volume=759 |issue=2 |page=145 |last1=Hoffman |first1=John|last2=Günther |first2=Hans M. |last3=Wright |first3=Nicholas J. |year=2012 |doi=10.1088/0004-637X/759/2/145 |s2cid=118365710}}</ref>

Several other stars have also been catalogued as companions to Capella.<ref name=wds/> Components I, Q and R are 13th-magnitude stars at distances of 92″, 133″ and 134″.<ref name=jdso2012>
{{cite journal
 |last1=Schlimmer |first1=J.
 |year=2010
 |title=Double star measurements using a webcam
 |series=Annual Report of 2009
 |journal=Journal of Double Star Observations
 |volume=6 |issue=3 |page=197
 |bibcode=2010JDSO....6..197S
}}
</ref> [[V538 Aurigae]] and its close companion HD&nbsp;233153 are red dwarfs ten degrees away from Capella; they have very similar space motions but the small difference makes it possible that this is just a coincidence.<ref name=shya>
{{cite journal
 |last1=Shaya |first1=Ed J.
 |last2=Olling |first2=Rob P.
 |year=2011
 |title=Very wide binaries and other co-moving stellar companions: A Bayesian analysis of the Hipparcos catalogue
 |journal=The Astrophysical Journal Supplement
 |volume=192 |issue=1 |page=2
 |doi=10.1088/0067-0049/192/1/2 |arxiv=1007.0425
 |bibcode=2011ApJS..192....2S |s2cid=119226823
}}</ref> Two faint stars have been discovered by [[speckle imaging]] in the Capella&nbsp;HL field, around 10″&nbsp;distant from that pair. These have been catalogued as Capella&nbsp;O and P. It is not known whether they are physically associated with the red dwarf binary.<ref name=helminiak>
{{cite journal
 |last1=Hełminiak |first1=K.G.
 |last2=Konacki |first2=M.
 |last3=Kulkarni |first3=S.R.
 |last4=Eisner |first4=J.
 |year=2009
 |title=Precision astrometry of a sample of speckle binaries and multiples with the adaptive optics facilities at the Hale and Keck&nbsp;II telescopes
 |journal=Monthly Notices of the Royal Astronomical Society
 |volume=400 |issue=1 |pages=406–421
 |doi=10.1111/j.1365-2966.2009.15495.x |doi-access=free
 |arxiv=0908.3468
 |s2cid=14169943 |bibcode=2009MNRAS.400..406H
}}
</ref>

==Etymology and culture==
Capella traditionally marks the left shoulder of the constellation's eponymous charioteer, or, according to the 2nd-century astronomer [[Ptolemy]]'s ''[[Almagest]]'', the goat that the charioteer is carrying. In Bayer's 1603 work ''[[Uranometria]]'', Capella marks the charioteer's back.<ref>{{cite book | last = Wagman | first = Morton | date = 2003 | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others | publisher = The McDonald & Woodward Publishing Company | isbn = 978-0-939923-78-6 |page=503}}</ref> The two ''[[Auriga (constellation)#Eclipsing binary stars|Haedi]]'' had been identified as a separate constellation by [[Pliny the Elder]] and [[Marcus Manilius|Manilius]], and were called ''Capra'', ''Caper'', or ''Hircus'', all of which relate to its status as the "goat star".{{sfn|Allen|2013|p=86}} [[Ptolemy]] merged the Charioteer and the Goats in the 2nd-century ''Almagest''.{{sfn|Winterburn|2009|p=131}}

In [[Greek mythology]], the star represented the goat [[Amalthea (mythology)|Amalthea]] that suckled [[Zeus]]. It was this goat whose horn, after accidentally being broken off by Zeus, was transformed into the [[cornucopia]], or "horn of plenty", which would be filled with whatever its owner desired.{{sfn|Schaaf |2008|p=152}} Though most often associated with Amalthea, Capella has sometimes been associated with Amalthea's owner, a [[nymph]]. The myth of the nymph says that the goat's hideous appearance, resembling a Gorgon, was partially responsible for the [[Titan (mythology)|Titans]]' defeat, after Zeus skinned the goat and wore it as his [[aegis]].<ref name="ridpathaur">{{cite web|url=http://www.ianridpath.com/startales/auriga.html|work=Star Tales|title=Auriga|author-link=Ian Ridpath|last1=Ridpath|first1=Ian|publisher=self-published|access-date=30 March 2022}}</ref>

In medieval accounts, it bore the uncommon name ''Alhajoth'' (also spelled ''Alhaior'', ''Althaiot'', ''Alhaiset'', ''Alhatod'', ''Alhojet'', ''Alanac'', ''Alanat'', ''Alioc''), which (especially the last) may be a corruption of its Arabic name, {{lang|ar|العيوق}}, ''al-<sup>c</sup>ayyūq.''{{sfn|Allen|2013|p=87}} ''<sup>c</sup>Ayyūq'' has no clear significance in Arabic,<ref>[[Edward William Lane]]'s Arabic-English Lexicon: {{sm|cwq}}</ref> but may be an Arabized form of the Greek αίξ ''aiks'' "goat"; cf. the modern Greek Αίγα ''Aiga'', the feminine of goat.{{sfn|Allen|2013|p=87}} To the [[Negev Bedouins|Bedouin]] of the [[Negev]] and [[Sinai Peninsula|Sinai]], Capella ''al-'Ayyūq ath-Thurayyā'' "Capella of the [[Pleiades]]", from its role as pointing out the position of that asterism.<ref>{{cite journal | jstor=613801 | title=Bedouin Star-Lore in Sinai and the Negev| first= Clinton| last= Bailey| journal=Bulletin of the School of Oriental and African Studies, University of London| volume=37| issue=3 | year=1974|pages= 580–96 | doi=10.1017/s0041977x00127491| s2cid=131527348}}</ref> Another name in Arabic was ''Al-Rākib'' "the driver", a translation of the Greek.{{sfn|Allen|2013|p=87}}

To the ancient [[Balts]], Capella was known as ''Perkūno Ožka'' "Thunder's Goat", or ''Tikutis''.<ref>{{cite journal | title=The Cosmology of the Ancient Balts | author1=Straižys, V. | author2=Klimka, L. | journal=Journal for the History of Astronomy, Archaeoastronomy Supplement | volume= 28| issue=22 |page=S57 |bibcode=1997JHAS...28...57S| year=1997 | doi=10.1177/002182869702802207| s2cid=117470993 }}</ref> Conversely in Slavic Macedonian folklore, Capella was ''Jastreb'' "the hawk", flying high above and ready to pounce on Mother Hen (the Pleiades) and the Rooster (Nath).<ref>{{cite journal|title=Macedonian Folk Constellations |author=Cenev, Gjore |journal=Publications of the Astronomical Observatory of Belgrade|volume= 85|pages=97–109|bibcode=2008POBeo..85...97C|year=2008 }}</ref>

[[Astrology|Astrologically]], Capella portends civic and [[military]] [[honor]]s and [[wealth]].{{sfn|Allen|2013|p=88}} In the [[Middle Ages]], it was considered a [[Behenian fixed star]], with the stone [[sapphire]] and the plants horehound, mint, mugwort and mandrake as attributes. [[Cornelius Agrippa]] listed its [[kabbalistic]] sign [[File:Agrippa1531 Hircus.png]] with the name ''Hircus'' (Latin for ''goat'').<ref>{{cite book|author=Henry Cornelius Agrippa|translator1=J. F.|year=2020|orig-year=Originally published 1651|title=The Philosophy of Natural Magic|url=https://books.google.com/books?id=Pk1MqGxY5GUC&pg=PT29|publisher=Library of Alexandria|isbn=978-1-4655-7650-7|page=29|access-date=2017-03-13|archive-date=2017-03-13|archive-url=https://web.archive.org/web/20170313134429/https://books.google.com/books?id=Pk1MqGxY5GUC&pg=PT29|url-status=live}}</ref><ref>{{cite book|author-link=Heinrich Cornelius Agrippa|author=Heinrich Cornelius Agrippa von Nettesheim|title=De Occulta Philosophia|url=https://books.google.com/books?id=HPIolNS-x4wC&pg=PA17|date=1967|orig-date=1533|publisher=Reichl Verlag|isbn=978-3-87667-021-8|page=17|language=la|access-date=2017-03-13|archive-date=2017-03-13|archive-url=https://web.archive.org/web/20170313125932/https://books.google.com/books?id=HPIolNS-x4wC&pg=PA17|url-status=live}}</ref>

In [[Hindu mythology]], Capella was seen as the heart of [[Brahma]], ''Brahma Hṛdaya''.{{sfn|Allen|2013|p=88}} In traditional [[Chinese astronomy]], Capella was part of the [[Asterism (astronomy)|asterism]] {{lang|zh|五車}} ({{lang|zh-Latn|Wŭ chē}}; English: ''[[Five Chariots]]''), which consisted of Capella together with [[Beta Aurigae]], [[Theta Aurigae]] and [[Iota Aurigae]], as well as [[Beta Tauri]].<ref>{{cite web |language=zh |url=http://aeea.nmns.edu.tw/2006/0607/ap060713.html |title=AEEA 天文教育資訊網, Activities of Exhibition and Education in Astronomy |publisher=National Museum of Natural Science, Taiwan. |access-date=31 December 2008 |archive-date=16 July 2011 |archive-url=https://web.archive.org/web/20110716123228/http://aeea.nmns.edu.tw/2006/0607/ap060713.html |url-status=live }}</ref><ref>{{cite book | title=Exploring Ancient Skies: An Encyclopedic Survey of Archaeoastronomy | first1= David H. | last1=Kelley|first2= E. F. |last2=Milone|first3= Anthony F. |last3=Aveni |publisher= Birkhäuser|year= 2005| isbn= 978-0-387-95310-6 | page= 322}}</ref> Since it was the second star in this asterism, it has the [[Chinese star names|Chinese name]] {{lang|zh|五車二}} ({{lang|zh-Latn|Wŭ chē èr}}; English: ''Second of the Five Chariots'').<ref>{{cite web | language=zh |url=http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_c_d.htm | title=香港太空 館 – 研究資源 – 亮星中英對照表 (Chinese/English Star names) |archive-url=https://web.archive.org/web/20090929163750/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_c_d.htm |archive-date=29 September 2009 |publisher=  Hong Kong Space Museum|access-date= 31 December 2008}}</ref> Capella's name in the [[Persian language|Persian]] astronomy is "Soroush".<ref>
{{cite web 
|url         = https://logatyab.ir/word/150085/%D8%B3%D8%B1%D9%88%D8%B4
|title       = معنی سروش چیست
|trans-title = What does Soroush mean
|language    = fa
|access-date = 26 March 2025
}}
</ref>

In [[Quechua language|Quechua]] it was known as ''Colça'';{{sfn|Allen|2013|p=88}} the Incas held the star in high regard.<ref>{{cite journal | title= L'Astronomie des Incas et des Anciens Peruviens | language=fr | author-link=E. M. Antoniadi|last= Antoniadi | first= E.M. |journal=L'Astronomie| volume= 56| pages=137–39 |bibcode=1942LAstr..56..137A| year=1942 }}</ref> The Hawaiians saw Capella as part of an asterism ''[[Ke Kā o Makaliʻi]]'' ("The canoe bailer of Makali'i") that helped them navigate at sea. Called ''Hoku-lei'' "star wreath" (or "star that rises like a cloud"<ref name="Vievard2023"/>), it formed this asterism with [[Procyon]], [[Sirius]], [[Castor (star)|Castor]] and [[Pollux (star)|Pollux]].{{sfn|Brosch|2008|p=46}} In Tahitian folklore, Capella was ''Tahi-ari'i'', the wife of ''Fa'a-nui'' (Auriga) and mother of prince ''Ta'urua'' ([[Venus]]) who sails his canoe across the sky.<ref name=henry1907>{{cite journal|last=Henry|first=Teuira|author-link=Teuira Henry |date=1907|title=Tahitian Astronomy: Birth of Heavenly Bodies|journal=The Journal of the Polynesian Society |volume=16|issue=2|pages=101–04|jstor=20700813}}</ref> In the [[Marshall Islands]], this star is Lōktañūr, the mother of ten sons represented by other stars.<ref>{{cite web |title=Leepwal |url=https://xing.fmi.uni-jena.de/mediawiki/index.php/Leepwal |website=All Skies Encyclopaedia |publisher=[[IAU Working Group on Star Names]] |access-date=12 May 2025}}</ref>

In [[Inuit astronomy]], Capella, along with Menkalinan ([[Beta Aurigae]]), [[Pollux (star)|Pollux]] (Beta Geminorum) and [[Castor (star)|Castor]] (Alpha Geminorum), formed a constellation [[Quturjuuk]], "collar-bones", the two pairs of stars denoting a bone each. Used for navigation and time-keeping at night, the constellation was recognised from [[Alaska]] to western Greenland.<ref>{{cite book | last = MacDonald | first = John | date = 1998 | title = The Arctic Sky: Inuit Astronomy, Star Lore, and Legend | url = https://archive.org/details/arcticskyinuitas0000macd | url-access = registration | publisher = Royal Ontario Museum/Nunavut Research Institute | isbn = 978-0-88854-427-8 |pages=[https://archive.org/details/arcticskyinuitas0000macd/page/65 65–67] }}</ref> The [[Gwich'in]] saw Capella and Menkalinan has forming ''shreets'ą įį vidzee'', the right ear of the large circumpolar constellation ''Yahdii'', which covered much of the night sky, and whose orientation facilitated navigation and timekeeping.<ref>{{cite journal|last1=Cannon|first1=Chris|first2=Gary|last2=Holton|title=A newly documented whole-sky circumpolar constellation in Alaskan Gwich'in|journal=[[Arctic Anthropology]]|volume=51|issue=2|year=2014|pages=1–8|url=https://par.nsf.gov/servlets/purl/10017304|doi=10.3368/aa.51.2.1|s2cid=164631823|access-date=2017-06-22|archive-date=2018-07-20|archive-url=https://web.archive.org/web/20180720110144/https://par.nsf.gov/servlets/purl/10017304|url-status=live}}</ref>

In [[Australian Aboriginal astronomy|Australian Aboriginal mythology]] for the [[Wergaia#Mythological and empirical thinking|Boorong]] people of Victoria, Capella was ''Purra'', the [[Kangaroo#Interaction with humans|kangaroo]], pursued and killed by the nearby Gemini twins, ''Yurree'' ([[Castor (star)|Castor]]) and ''Wanjel'' ([[Pollux (star)|Pollux]]).<ref>{{cite journal|bibcode=1857PPIVT...2..137S|page=140|title=On the astronomy and mythology of the Aborigines of Victoria|journal=Proceedings of the Philosophical Institute of Victoria|volume=2|last1=Stanbridge|first1=William Edward|year=1857}}</ref> The [[Wardaman people]] of northern Australia knew the star as ''Yagalal'', a ceremonial fish scale, related to Guwamba the [[barramundi]] ([[Aldebaran]]).<ref>{{cite book | last1 = Harney | first1 = Bill Yidumduma | last2 = Cairns | first2 = Hugh C. | title = Dark Sparklers | publisher = Hugh C. Cairns |pages=204–05 | date = 2004 | orig-date = 2003 | edition = Revised | isbn = 978-0-9750908-0-0}}</ref>

===Namesakes===
* {{USS|Capella|AK-13}} and [[SS Capella (T-AKR-293)|USNS ''Capella'' (T-AKR-293)]], both [[U.S. Navy]] ships
* [[Mazda Capella]], a model of automobile manufactured by [[Mazda]]

==See also==
* [[List of brightest stars]]
* [[List of nearest bright stars]]
* [[Historical brightest stars]]
* [[List of nearest giant stars]]

==Notes==
{{reflist|group=note}}

==References==
{{Reflist|refs=

<ref name=webster>{{cite web
 | title=Capella
 | publisher=Merriam-Webster
 | url=https://www.merriam-webster.com/dictionary/Capella
 | access-date=2022-05-09 }}</ref>

<ref name=petit>{{cite journal|bibcode=1990A&AS...85..971P|title=Catalogue of Variable or Suspected Stars Nearby the Sun|journal=Astronomy and Astrophysics Supplement|volume=85|page=971|last1=Petit|first1=M.|year=1990}}</ref>

<ref name=eggen>{{cite journal|bibcode=1963AJ.....68..483E|title=Three-color photometry of the components in 228 wide double and multiple systems|journal=Astronomical Journal|volume=68|page=483|author-link=Olin Eggen|last1=Eggen|first1=Olin J.|year=1963|doi=10.1086/109000}}</ref>

<ref name=agrawal>{{cite journal|bibcode=1986MNRAS.219..225A|title=Study of quiescent state X-ray emission from flare stars|journal=Monthly Notices of the Royal Astronomical Society|issn=0035-8711|volume=219|issue=2|page=225|last1=Agrawal|first1=P. C.|last2=Rao|first2=A. R.|last3=Sreekantan|first3=B. V.|year=1986|doi=10.1093/mnras/219.2.225|doi-access=free}}</ref>

<ref name=ppm>{{cite journal|bibcode=1988A&AS...74..449R|title=A new star catalogue of SAO type|journal=Astronomy and Astrophysics Supplement Series|issn=0365-0138|volume=74|page=449|last1=Roeser|first1=S.|last2=Bastian|first2=U.|year=1988}}</ref>

<ref name=2mass>{{cite journal |bibcode=2003yCat.2246....0C |title=VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) |journal=CDS/ADC Collection of Electronic Catalogues |pages=II/246 |volume=2246 |last1=Cutri |first1=Roc M. |last2=Skrutskie |first2=Michael F. |last3=Van Dyk |first3=Schuyler D. |last4=Beichman |first4=Charles A. |last5=Carpenter |first5=John M. |last6=Chester |first6=Thomas |last7=Cambresy |first7=Laurent |last8=Evans |first8=Tracey E. |last9=Fowler |first9=John W. |last10=Gizis |first10=John E. |last11=Howard |first11=Elizabeth V. |last12=Huchra |first12=John P. |last13=Jarrett |first13=Thomas H. |last14=Kopan |first14=Eugene L. |last15=Kirkpatrick |first15=J. Davy |last16=Light |first16=Robert M. |last17=Marsh |first17=Kenneth A. |last18=McCallon |first18=Howard L. |last19=Schneider |first19=Stephen E. |last20=Stiening |first20=Rae |last21=Sykes |first21=Matthew J. |last22=Weinberg |first22=Martin D. |last23=Wheaton |first23=William A. |last24=Wheelock |first24=Sherry L. |last25=Zacarias |first25=N. |year=2003 |url=http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=II/246 }}</ref>

<ref name=perkins>{{cite journal|bibcode=1989ApJS...71..245K|title=The Perkins Catalog of Revised MK Types for the Cooler Stars|journal=The Astrophysical Journal Supplement Series|volume=71|page=245|last1=Keenan|first1=Philip C|last2=McNeil|first2=Raymond C|year=1989|doi=10.1086/191373}}</ref>

<ref name=hr>{{cite journal|bibcode=1991bsc..book.....H|title=The Bright star catalogue|journal=New Haven, Conn.: Yale University Observatory, 5th Rev.ed.|year=1991|author-link1=Dorrit Hoffleit|last1=Hoffleit|first1=Dorrit|last2=Jaschek|first2=Carlos}}</ref>

<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=B/GCVS|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>

<ref name=strassmeier>{{cite journal|bibcode=1990A&A...230..389S|title=The spectral classification of chromospherically active binary stars with composite spectra|journal=Astronomy and Astrophysics|volume=230|page=389|last1=Strassmeier|first1=K. G.|last2=Fekel|first2=F. C.|year=1990}}</ref>

<ref name=joy>{{cite journal|bibcode=1974ApJS...28....1J|title=Spectral Types of M Dwarf Stars|journal=Astrophysical Journal Supplement|volume=28|page=1|author-link=Alfred Harrison Joy|last1=Joy|first1=Alfred H.|last2=Abt|first2=Helmut A.|year=1974|doi=10.1086/190307}}</ref>

<ref name=stauffer>{{cite journal|bibcode=1986ApJS...61..531S|doi=10.1086/191123|title=Chromospheric activity, kinematics, and metallicities of nearby M dwarfs|journal=The Astrophysical Journal Supplement Series|volume=61|page=531|year=1986|last1=Stauffer|first1=J. R.|last2=Hartmann|first2=L. W.|doi-access=free}}; see Table 1.</ref>

<ref name=gliese>[http://webviz.u-strasbg.fr/viz-bin/VizieR-S?GJ%20195 GJ 195] {{Webarchive|url=https://web.archive.org/web/20171107165957/http://webviz.u-strasbg.fr/viz-bin/VizieR-S?GJ%20195 |date=2017-11-07 }}, catalog entry, ''Preliminary Version of the Third Catalogue of Nearby Stars'', [[Wilhelm Gliese|Gliese, Wilhelm]]; Jahreiss, H. 1991, [[Centre de Données astronomiques de Strasbourg|CDS]] ID [http://cdsarc.u-strasbg.fr/viz-bin/Cat?V/70A V/70A] {{Webarchive|url=https://web.archive.org/web/20080531090923/http://cdsarc.u-strasbg.fr/viz-bin/Cat?V%2F70A |date=2008-05-31 }}.</ref>

<ref name=bidelman>{{cite journal|bibcode=1985ApJS...59..197B|title=G. P. Kuiper's spectral classifications of proper-motion stars|journal=Astrophysical Journal Supplement Series|issn=0067-0049|volume=59|page=197|last1=Bidelman|first1=W. P.|year=1985|doi=10.1086/191069|doi-access=free}}</ref>

<ref name=torres15>{{cite journal|bibcode=2015ApJ...807...26T|arxiv=1505.07461|title=Capella (α Aurigae) Revisited: New Binary Orbit, Physical Properties, and Evolutionary State|journal=The Astrophysical Journal|volume=807|issue=1|page=26|last1=Torres|first1=Guillermo|last2=Claret|first2=Antonio|last3=Pavlovski|first3=Krešimir|last4=Dotter|first4=Aaron|year=2015|doi=10.1088/0004-637X/807/1/26|s2cid=55901109}}</ref>

<ref name="Gaia3h">{{cite Gaia DR3|211810233512673792}}</ref>

<ref name="Gaia3l">{{cite Gaia DR3|211810233512673920}}</ref>

<ref name=Johnson1983>{{cite journal|bibcode=1983ApJ...273..702J|title=Origins and ages of X-ray-luminous dwarf M stars|journal=Astrophysical Journal|volume=273|page=702|last1=Johnson|first1=H.M.|year=1983|doi=10.1086/161405|doi-access=free}}</ref>

<ref name=gaiadr2l>{{cite DR2|211810233512673920}}</ref>

<ref name=gaiadr2h>{{cite DR2|211810233512673792}}</ref>

<ref name=mult>{{cite journal|bibcode=1992ApJ...396..178F|doi=10.1086/171708|title=Multiplicity among M dwarfs|journal=The Astrophysical Journal|volume=396|page=178|year=1992|author-link=Debra Fischer|last1=Fischer|first1=Debra A.|last2=Marcy|first2=Geoffrey W.|doi-access=free}}; see Table 1.</ref>

<ref name=lowmass>{{cite journal|bibcode=1996ApJS..104..117L|doi=10.1086/192295|title=Infrared Spectra of Low-Mass Stars: Toward a Temperature Scale for Red Dwarfs|journal=The Astrophysical Journal Supplement Series|volume=104|page=117|year=1996|last1=Leggett|first1=S. K.|last2=Allard|first2=F.|last3=Berriman|first3=Graham|last4=Dahn|first4=Conard C.|last5=Hauschildt|first5=Peter H.|s2cid=121534198}}; see Tables 3, 6 and 7.</ref>

<ref name=sb0>{{SIMBAD link|alf+aur|NAME CAPELLA – Variable of RS CVn type}}, database entry, [[SIMBAD]].  Accessed online December 23, 2008.</ref>

<ref name=sb1>{{SIMBAD link|CCDM+J05168%2B4559H|G 96-29 – High proper-motion Star}}, database entry, [[SIMBAD]]. Accessed online December 23, 2008.</ref>

<ref name=sb2>{{SIMBAD link|CCDM+J05168%2B4559L|NAME CAPELLA L – Star in double system}}, database entry, [[SIMBAD]]. Accessed online December 23, 2008.</ref>

<ref name="Vievard2023">{{cite journal |last1=Vievard |first1=S. |last2=Huby |first2=E. |display-authors=etal |date=September 2023 |title=Single-aperture spectro-interferometry in the visible at the Subaru telescope with FIRST: First on-sky demonstration on Keho'oea (α Lyrae) and Hokulei (α Aurigae) |journal=[[Astronomy & Astrophysics]] |volume=677 |issue= |pages=A84 |doi=10.1051/0004-6361/202245115 |arxiv=2307.09746 |bibcode=2023A&A...677A..84V}}</ref>

}}

==Sources==
* {{cite book | last=Allen |first=Richard Hinckley | author-link=Richard Hinckley Allen | date=2013 |orig-date=1899 | title=Star Names: Their Lore and Meaning | edition=[[Reprint]] | publisher=Courier Corporation | isbn=978-0-486-13766-7 }}
* {{cite book|last=Burnham |first=Robert Jr. | author-link=Robert Burnham Jr. |title=Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Volume One: Andromeda-Cetus|edition=Revised & Enlarged|year=1978|publisher=Dover Publications|isbn=978-0-486-23567-7 }}
* {{cite book
 | author-link = Ian Ridpath
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 | first2 = Wil
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* {{cite book|author-link=Noah Brosch|author=Brosch |first1=Noah |title=Sirius Matters|url=https://books.google.com/books?id=ricStR4SE-UC&pg=PR9|date= 2008|publisher=Springer Science & Business Media|isbn=978-1-4020-8319-8}}
* {{cite book|isbn=978-0-470-24917-8|title=The Brightest Stars: Discovering the Universe through the Sky's Most Brilliant Stars|publisher=Wiley |last1=Schaaf|first1=Fred|year=2008 }}
* {{cite book | last = Winterburn | first = Emily | date = 2009 | title = The Stargazer's Guide: How to Read Our Night Sky | publisher = Harper Perennial | isbn = 978-0-06-178969-4 }}
{{Sky|05|16|41.3591||45|59|52.768|42}}

{{Stars of Auriga}}
{{Portal bar|Astronomy|Stars|Outer space}}

<!-- Properties -->

{{DEFAULTSORT:Capella}}
[[Category:G-type giants]]
[[Category:K-type giants]]
[[Category:M-type main-sequence stars]]
[[Category:RS Canum Venaticorum variables]]
[[Category:Astronomical X-ray sources]]
[[Category:Spectroscopic binaries]]
[[Category:Multiple star systems|4]]
[[Category:Hyades Stream]]
<!-- Identifiers -->
[[Category:Auriga]]
[[Category:Bayer objects|Aurigae, Alpha]]
[[Category:Bright Star Catalogue objects|1708]]
[[Category:Durchmusterung objects|BD+45 1077]]
[[Category:Flamsteed objects|Aurigae, 13]]
[[Category:Gliese and GJ objects|0194]]
[[Category:Henry Draper Catalogue objects|034029]]
[[Category:Hipparcos objects|024608]]
[[Category:Stars with proper names]]
[[Category:Population I stars]]
[[Category:Lucidae]]