Editing Epsilon Cygni

{{short description|Star in the constellation Cygnus}}
{{Starbox begin
| name=Epsilon Cygni
}}
{{Starbox image
 | image=
{{Location mark
|image=Cygnus constellation map.svg
|float=center
|alt=
|label=
|position=right
|width=280
|mark=Red circle.svg
|mark_width=12
|mark_link=ε Cygni
|x=273|y=553
}}
|caption=Location of ε Cyg (circled)
}}
{{Starbox observe
| epoch=J2000
| ra={{RA|20|46|12.68236}}<ref name="aaa474_2_653" />
| dec={{DEC|+33|58|12.9250}}<ref name="aaa474_2_653" />
| appmag_v=2.480<ref name="aaass65_2_405" />
| constell=[[Cygnus (constellation)|Cygnus]]
}}
{{Starbox character
| type = [[Horizontal branch]]<ref name=Heeren2021/>
| class=K0&nbsp;III<ref name="Gray">{{cite journal|bibcode=2015ApJ...810..117G | doi=10.1088/0004-637X/810/2/117 | title=A Spectroscopic Analysis of the K0 III Binary ε Cygni | journal=The Astrophysical Journal | volume=810 | issue=2 | pages=117 | year=2015 | last1=Gray | first1=David F.| s2cid=125700196 | doi-access=free }}</ref>
| b-v=+1.030<ref name="aaass65_2_405" />
| u-b=+0.860<ref name="aaass65_2_405" />
| variable=
}}
{{Starbox astrometry
| radial_v=−12.41<ref name="aj135_1_209" />
| prop_mo_ra=355.66<ref name="aaa474_2_653" />
| prop_mo_dec=330.60<ref name="aaa474_2_653" />
| parallax=44.86
| p_error=0.12
| parallax_footnote=<ref name="aaa474_2_653" />
| absmag_v={{nowrap|+0.74 ± 0.02}}<ref name="Gray" />
}}
{{Starbox orbit
| reference=<ref name=Heeren2021/>
| primary=ε Cyg Aa
| name=ε Cyg Ab
| period= {{val|{{convert|19611.5|day|year|disp=number}}|{{convert|117.4|day|year|disp=number}}|{{convert|119.9|day|year|disp=number}}}}
| axis_unitless = {{val|15.8|0.2|ul=AU}}
| k1=4.6
| eccentricity= {{val|0.9295|0.0003}}
| periarg_primary = {{val|275.30|0.06}}
}}
{{Starbox detail
| component1 = A
| mass= {{val|1.103|0.042}}<ref name=Heeren2021/>
| radius=11.13<ref name=Gray2019/>
| luminosity={{val|56.4|0.6}}<ref name="da Silva"/>
| temperature=4,699<ref name=Gray2019/>
| metal_fe={{val|-0.126}}<ref name=Gray2019/>
| gravity={{val|2.79|0.23}}<ref name="da Silva"/>
| rotational_velocity={{nowrap|2.3 ± 0.2}}<ref name="Gray" />
| rotation={{val|0.67}}<ref name="Gray" /> years
| age_gyr = {{val|9.62|0.12}}<ref name=Heeren2021/>
| component2 = B
| mass2 = {{val|0.265|0.007|p=≥}}<ref name=Heeren2021/>
}}
{{Starbox catalog
| names=Aljanah, Gienah,<ref name="rumrill">{{cite journal|bibcode=1936PASP...48..139R|title=Star Name Pronunciation|journal=Publications of the Astronomical Society of the Pacific|volume=48|issue=283|pages=139|last1=Rumrill|first1=H. B.|year=1936|doi=10.1086/124681|s2cid=120743052 |doi-access=free}}</ref> ε Cyg, 53&nbsp;Cygni, [[Bonner Durchmusterung|BD]]+33°4018, [[FK5]]&nbsp;780, [[General Catalogue of Trigonometric Parallaxes|GCTP]]&nbsp;4959.00, [[Gliese Catalogue of Nearby Stars|Gl]]&nbsp;806.1, [[Henry Draper catalogue|HD]]&nbsp;197989, [[Hipparcos catalogue|HIP]]&nbsp;102488, [[Harvard Revised catalogue|HR]]&nbsp;7949, [[Luyten Half-Second catalogue|LHS]]&nbsp;5358, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;70474, [[Washington Double Star Catalog|WDS]] 20462+3358<ref name="SIMBAD" />
}}
{{Starbox reference
| Simbad=HD+197989
}}
{{Starbox end}}
'''Epsilon Cygni''' ('''ε Cygni''', abbreviated '''Epsilon Cyg''', '''ε Cyg''') is [[binary star]] in the [[constellation]] of [[Cygnus (constellation)|Cygnus]]. With an [[apparent magnitude|apparent visual magnitude]] of 2.48, it is [[Bortle scale|readily visible]] to the naked eye at night, and is the [[List of stars in Cygnus|third-brightest star]] in the constellation. Based upon [[stellar parallax|parallax]] measurement, Epsilon Cygni is about 73 [[light-year]]s distant.

The system has two confirmed constituents, Epsilon Cygni Aa (officially named '''Aljanah''' {{IPAc-en|'|æ|l|dʒ|ə|n|ə}})<!--since the first two vowels are short, this is the expected Latinized pronunciation. Could imagine al-JEE-n@ by analogy with Gienah, but few are aware of the correspondence.--> and Ab. Additionally, a visual companion (Epsilon Cygni C) is likely bound to the system.<ref name=Heeren2021/>

== Nomenclature ==
''ε Cygni'' ([[Latinisation of names|Latinised]] to ''Epsilon Cygni'') is the system's [[Bayer designation]]. The designations of the three constituents as ''Epsilon Cygni A'', ''B'' and ''C'', and those of ''A's'' components - ''Epsilon Cygni Aa'' and ''Ab'' - derive from the convention used by the Washington Multiplicity Catalog (WMC) for [[Star system|multiple star system]]s, and adopted by the [[International Astronomical Union]] (IAU).<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U.}}</ref>

Epsilon Cygni bore the traditional name ''Gienah'' from the [[Arabic]] ''al janāħ'' ({{langx|ar|جناح}}) meaning "the [[wing]]".<ref name="hinkley1899" /> However that name was more usually applied to [[Gamma Corvi]].<ref name="rumrill" /> For reasons of disambiguation it was sometimes called Gienah Cygni. In 2016, the IAU organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire [[multiple star|multiple systems]].<ref name="TriRpt18">{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |access-date=2018-07-14}}</ref> It approved the name ''Aljanah'' for the component Epsilon Cygni Aa on 30 June 2017. It had previously approved the name ''Gienah'' for Gamma Corvi A on 6 November 2016. Both are now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN" />

In [[Chinese astronomy]], the "[[Girl (Chinese constellation)|Celestial Ford]]" ({{zh|c=天津|p=Tiān Jīn}}) refers to an [[Asterism (astronomy)|asterism]] consisting of Epsilon Cygni, [[Gamma Cygni]], [[Delta Cygni]], [[30 Cygni]], [[Deneb|Alpha Cygni]], [[Nu Cygni]], [[Tau Cygni]], [[Upsilon Cygni]] and [[Zeta Cygni]].<ref name="G1zAz">{{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}}.</ref> Consequently, the [[Chinese star names|Chinese name]] for Epsilon Cygni Cygni itself is "the Ninth Star of Celestial Ford" ({{zh|c=天津九|p=Tiān Jīn jiǔ}}).<ref name="5g83o">{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_e_g.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20110130063007/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_e_g.htm |date=2011-01-30}}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>

==Companions==
Epsilon Cygni A has an optical companion, Epsilon Cygni B, with which it is not physically associated, and a 13th magnitude candidate common [[proper motion]] companion, Epsilon Cygni C, at an angular separation of 78 [[Minute and second of arc|arcseconds]].<ref name="pasp104_682_1173" /> If the latter star is [[gravitational binding energy|gravitationally bound]] to Epsilon Cygni A, then they are currently separated by 1,700&nbsp;[[Astronomical unit|AU]] or more, and have an [[orbital period]] of at least 50,000 years.<ref name="kaler" />

== Properties ==
[[File:Cygnus 70 panel Mosaic in H-Alpha.jpg|thumb|left|upright|ε Cygni appears north of the [[Veil nebula]] towards the bottom left]]
Epsilon Cygni A is a [[binary star#Spectroscopic binaries|single-lined spectroscopic binary]].<ref name="WDS" /> The components take 53 years to complete an orbit and are in a highly [[orbital eccentricity|eccentric]] orbit, which put their distances from 1.1&nbsp;[[astronomical unit]]s in [[apoapsis]] to 30.5&nbsp;astronomical units in [[periapsis]].<ref name=Heeren2021/>{{efn|name=ecc|1=Calculated using semi-major axis of 15.8 AU and eccentricity of 0.93 via the equations SMA(1&minus;''e'') for apoastron and SMA(1+''e'') for periastron.}} Its main component is a [[giant star]] with a [[stellar classification]] of K0&nbsp;III.<ref name="aj117_4_1864" /> This indicates that the star has left the [[main sequence]] and has begun the final stages in its [[stellar evolution]]. After passing through the [[red-giant branch]] stage, it underwent a [[helium flash]] event and is now a [[horizontal branch]] star generating energy through the [[thermonuclear fusion]] of helium at its [[stellar core|core]].<ref name=Heeren2021/> The [[effective temperature]] of its [[photosphere]] is 4,700 K,<ref name=Gray2019/> giving an orange hue that is a characteristic of [[stellar classification#Class K|K-type]] stars.<ref name="csiro" /> Being 10% more massive than the Sun and nine billion years old,<ref name=Heeren2021/> It has 11 times the [[solar radius|radius of the Sun]]<ref name=Gray2019/> and is about 56 times more luminous.<ref name="da Silva"/>

The secondary has never been observed directly, its existence was inferred solely on [[astronomical spectroscopy]]. Based on this data, it should have a mass of at least {{solar mass|0.265|unit=y}}.<ref name=Heeren2021/>

Since 1943, the [[stellar spectrum|spectrum]] of Epsilon Cygni A has served as one of the stable anchor points by which other stars are classified.<ref name="baas25_1319" />

==Veil Nebula==
{{main|Veil nebula}}
ε Cygni lies about three degrees north of the [[Veil nebula]], a probable ancient [[supernova remnant]].  The nebula is far more distant than the star.

== Notes ==
<references group="lower-alpha" />
==References==
{{reflist|refs=

<ref name="da Silva">{{Citation |last=da Silva |first=Ronaldo |last2=Milone |first2=André de C. |last3=Rocha-Pinto |first3=Helio J. |date=2015-08-01 |title=Homogeneous abundance analysis of FGK dwarf, subgiant, and giant stars with and without giant planets |bibcode=2015A&A...580A..24D |journal=Astronomy and Astrophysics |volume=580 |pages=A24 |doi=10.1051/0004-6361/201525770 |issn=0004-6361|arxiv=1505.01726 }} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/A%2BA/580/A24&Name=HD197989 Epsilon Cygni's database entry] at [[VizieR]].</ref>

<ref name=Gray2019>{{Citation |last1=Gray |first1=David F. |last2=Kaur |first2=Taranpreet |date=2019-09-01 |title=A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines |journal=The Astrophysical Journal |volume=882 |issue=2 |pages=148 |doi=10.3847/1538-4357/ab2fce |doi-access=free |bibcode=2019ApJ...882..148G |issn=0004-637X}}</ref>

<ref name=Heeren2021>{{Citation |last=Heeren |first=Paul |last2=Reffert |first2=Sabine |last3=Trifonov |first3=Trifon |last4=Wong |first4=Ka Ho |last5=Lee |first5=Man Hoi |last6=Lillo-Box |first6=Jorge |last7=Quirrenbach |first7=Andreas |last8=Arentoft |first8=Torben |last9=Albrecht |first9=Simon |last10=Grundahl |first10=Frank |last11=Andersen |first11=Mads Fredslund |last12=Antoci |first12=Victoria |last13=Pallé |first13=Pere L. |date=2021-03-01 |title=Precise radial velocities of giant stars - XV. Mysterious nearly periodic radial velocity variations in the eccentric binary ε Cygni |journal=Astronomy & Astrophysics |language=en |volume=647 |pages=A160 |doi=10.1051/0004-6361/202040087 |bibcode=2021A&A...647A.160H |issn=0004-6361|arxiv=2102.01999 }}</ref>

<ref name="aaa474_2_653">{{citation | first1=Floor | last1=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | arxiv=0708.1752v1 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics| s2cid=18759600 }} ''Note:'' see VizieR catalogue [http://vizier.u-strasbg.fr/viz-bin/Cat?I/311 I/311].</ref>

<ref name="aj135_1_209">{{citation | display-authors=1 | last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W. | last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey | title=Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity | journal=The Astronomical Journal | volume=135 | issue=1 | pages=209–231 |date=January 2008 | doi=10.1088/0004-6256/135/1/209 | bibcode=2008AJ....135..209M| doi-access=free }}</ref>

<ref name="aaass65_2_405">{{citation | last1=Oja | first1=T. | title=UBV photometry of stars whose positions are accurately known. III | journal=Astronomy and Astrophysics Supplement Series | volume=65 | issue=2 | pages=405–409 |date=August 1986 | bibcode=1986A&AS...65..405O}}</ref>

<ref name="SIMBAD">{{citation | title=LHS 5358b -- High proper-motion Star | work=SIMBAD | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Epsilon+Cygni | access-date=2011-12-10}}</ref>

<ref name="pasp104_682_1173">{{citation | last1=McMillan | first1=R. S. | last2=Smith | first2=P. H. | last3=Moore | first3=T. L. | last4=Perry | first4=M. L. | title=Variation of the radial velocity of Epsilon Cygni A | journal=Publications of the Astronomical Society of the Pacific | volume=104 | issue=682 | pages=1173–1176 |date=December 1992 | doi=10.1086/133105 | bibcode=1992PASP..104.1173M| doi-access=free }}</ref>

<ref name="aj117_4_1864">{{citation | display-authors=1 | last1=Cohen | first1=Martin | last2=Walker | first2=Russell G. | last3=Carter | first3=Brian | last4=Hammersley | first4=Peter | last5=Kidger | first5=Mark | last6=Noguchi | first6=Kunio | title=Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra | journal=The Astronomical Journal | volume=117 | issue=4 | pages=1864–1889 |date=April 1999 | doi=10.1086/300813 | bibcode=1999AJ....117.1864C| doi-access=free }}</ref>

<ref name="kaler">{{citation | first1=James | last1=Kaler | work=Stars | publisher=[[University of Illinois]] | title=GIENAH CYGNI (Epsilon Cygni) | url=http://stars.astro.illinois.edu/sow/gienahcyg.html | access-date=2011-12-11}}</ref>

<ref name="hinkley1899">{{citation | first1=Richard Hinckley | last1=Allen | title=Star-names and their meanings | journal=New York | publisher=G.E. Stechert | year=1899 | page=197 | url=https://books.google.com/books?id=5xQuAAAAIAAJ&pg=PA197 | bibcode=1899sntm.book.....A}}</ref>

<ref name="csiro">{{citation |title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=[[Commonwealth Scientific and Industrial Research Organisation]] |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |access-date=2012-01-16 |url-status=dead |archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=2012-03-18}}</ref>

<ref name="baas25_1319">{{citation | last1=Garrison | first1=R. F. | title=Anchor Points for the MK System of Spectral Classification | journal=Bulletin of the American Astronomical Society | volume=25 | page=1319 | date=December 1993 | bibcode=1993AAS...183.1710G | url=http://www.astro.utoronto.ca/~garrison/mkstds.html | access-date=2012-02-04 | archive-date=2019-06-25 | archive-url=https://web.archive.org/web/20190625094716/http://www.astro.utoronto.ca/~garrison/mkstds.html | url-status=dead }}</ref>

<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=16 December 2017}}</ref>

<ref name="WDS">{{cite web | url=http://ad.usno.navy.mil/wds/ | title=Washington Double Star Catalog | publisher=United States Naval Observatory | access-date=2 January 2018 | archive-url=https://web.archive.org/web/20110214155533/http://ad.usno.navy.mil/wds/ | archive-date=14 February 2011 | url-status=dead}}</ref>

}}

==External links==
* http://www.pbase.com/mcrowle/image/81902791

{{Stars of Cygnus}}

[[Category:Bayer objects|Cygni, Epsilon]]
[[Category:Cygnus (constellation)]]
[[Category:K-type giants]]
[[Category:Stars with proper names|Aljanah]]
[[Category:Flamsteed objects|Cygni, 53]]
[[Category:Bright Star Catalogue objects|7949]]
[[Category:Henry Draper Catalogue objects|197989]]
[[Category:Hipparcos objects|102488]]
[[Category:Durchmusterung objects|BD+33 4018]]
[[Category:Gliese and GJ objects|0806.1]]
[[Category:Multiple stars]]
[[Category:Horizontal-branch stars]]