Delta Cygni

{{short description|Third-magnitude star in the constellation Cygnus}} {{Starbox begin | name = δ Cygni }} {{Starbox image | image= {{Location mark |image=Cygnus constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=δ Cygni |x=546|y=319 }} |caption=Location of δ Cygni (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|19|44|58.47854}}<ref name=aaa474_2_653/> | dec = {{DEC|+45|07|50.9161}}<ref name=aaa474_2_653/> | appmag_v = 2.87<ref name=aass85_3_1015/> | constell = Cygnus }} {{Starbox character | class = A0 IV<ref name=bcd/> {{nowrap|(B9 III + F1 V<ref name=aj81_245/>)}} | b-v = −0.02<ref name=clpl4_99/> | u-b = −0.10<ref name=clpl4_99/> | variable = Suspected<ref name=nsv/> }} {{Starbox astrometry | radial_v = −20.1<ref name=rgcrv/> | prop_mo_ra = +44.07<ref name=aaa474_2_653/> | prop_mo_dec = +48.66<ref name=aaa474_2_653/> | parallax = 19.77 | p_error = 0.48 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = −0.74<ref name=Anderson2012/> }} {{Starbox orbit | reference = <ref name=malkov/> | primary = A | name = B | period = 780.27 | eccentricity = 0.4670 | inclination = | axis = 3.0 }} {{Starbox detail | source = <ref name=challouf2014/> | mass = 2.93 | radius = {{val|4.81|0.36}}<ref name="gordon2019"/> | luminosity = 155 | temperature = {{val|10,400|400}}<ref name="gordon2019"/> | gravity = {{val|3.4|0.25}}<ref name="gordon2019"/> | metal_fe = | rotational_velocity = 142<ref name="gordon2019"/> }} {{Starbox catalog | names = {{odlist | name=Fawaris | B=δ Cyg | F=18 Cygni, 18 Cyg | BD=+44°3234 | HD=186882 | HIP=97165 | HR=7528 | SAO=48796 | WDS=J19450+4508AB }} }} {{Starbox reference|Simbad=del+Cyg}} {{Starbox end}}

'''Delta Cygni''' is a binary star of a combined third-magnitude in the constellation of Cygnus. It is also part of the Northern Cross asterism whose brightest star is Deneb. Its name is a Bayer designation that is Latinized from '''δ Cygni''', and abbreviated Delta Cyg or δ Cyg. Based upon parallax measurements obtained during the Hipparcos mission, Delta Cygni is located roughly {{Convert|165|ly|pc|abbr=off|lk=on}} distant from the Sun.<ref name=aaa474_2_653/>

Delta Cygni's two components are designated Delta Cygni A (officially named '''Fawaris''' {{IPAc-en|f|@|'|w|ɛər|ɪ|s}})<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars | publisher=IAU.org | access-date=18 June 2018 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref> and B. More widely separated is a faint third component, a 12th magnitude star that is moving along with the others. Together they form a triple star system.<ref name=kalerAC/>

== Nomenclature ==

''δ Cygni'' (Latinised to ''Delta Cygni'') is the binary's Bayer designation. The designations of the two components as ''Delta Cygni A'' and ''B'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, 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>

Traditionally, Delta Cygni had no proper name.<ref name="kalerAC"/> It belonged to the Arabic asterism ''al-Fawāris'' ({{lang|ar|الفوارس}}), meaning "the Riders" in indigenous Arabic,<ref>{{cite book | last=Allen | first=R. H. | year=1963 | author-link=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | edition=Reprint | publisher=Dover Publications Inc. | location=New York, NY | isbn=978-0-486-21079-7 | pages=[https://archive.org/details/starnamestheirlo00alle/page/193 193], 197| title-link=Star Names: Their Lore and Meaning }}</ref> together with Zeta, Epsilon, and Gamma Cygni, the transverse of the Northern Cross. In 2016, the IAU organized a 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 | 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=dead }}</ref> to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire 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 | archive-date=2019-08-23 | archive-url=https://web.archive.org/web/20190823174756/https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | url-status=dead }}</ref> It approved the name ''Fawaris'' for the component Delta Cygni A on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>

In Chinese, {{lang|zh|天津}} ({{lang|zh-Latn|Tiān Jīn}}), meaning ''Celestial Ford'', refers to an asterism consisting of Delta Cygni, Gamma Cygni, 30 Cygni, Alpha Cygni (Deneb) and Nu, Tau, Upsilon, Zeta and Epsilon Cygni.<ref>{{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 name for Delta Cygni itself is {{lang|zh|天津二}} ({{lang|zh-Latn|Tiān Jīn èr}}, {{langx|en|the Second Star of Celestial Ford}}).<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060704.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 4 日] {{Webarchive|url=https://web.archive.org/web/20110522123616/http://aeea.nmns.edu.tw/2006/0607/ap060704.html |date=2011-05-22 }}</ref> {{See also|Cygnus (Chinese astronomy)}}

== Properties ==

The primary, Delta Cygni A, is a blue-white giant star of spectral class B9,<ref name=aj81_245/> with a temperature of 10,400 K.<ref name="gordon2019"/> It is nearing the end of its main-sequence life stage with a luminosity 155 times that of the Sun,<ref name=challouf2014/> a radius of 4.81 solar radii,<ref name="gordon2019"/> and a mass approximately 2.93 solar masses. Like many hot stars, it spins rapidly, at least 135 kilometers per second at the equator, about 60 times that of the Sun.<ref name=challouf2014/>

The close companion Delta Cygni B is a yellow-white F-type main-sequence star of the sixth magnitude (6.33) with a luminosity about 6 times that of the Sun, and a mass about 1.5 times the Sun's. The two stars orbit each other at an average distance of 157 AU and a period of 780 years.<ref name=kalerAC/>

The much more distant third companion is an orange (class K) twelfth magnitude star, and only two thirds as massive.<ref name="kalerAC"/>

The two main stars together appear with a spectral type of A0 IV.<ref name=bcd/> As seen from Earth, the entire triple star system of Delta Cygni shines at a combined apparent magnitude of 2.87.<ref name=aass85_3_1015/> Both δ Cygni A and B have been suspected to vary in brightness. δ Cygni A was reported in 1951 as varying between magnitudes 2.85 and 2.89, and δ Cygni B was reported in 1837 to vary between magnitudes 6.3 and 8.5. The variability of the stars has not been confirmed.<ref name=nsv/>

== Pole Star == {{main|Pole star}} Delta Cygni is a visible star located within 3° of the precessional path traced across the celestial sphere by the Earth's North pole. For at least four centuries around 11,250 AD it will probably be considered a pole star, a title currently held by Polaris which is just 0.5° off of the precessional path.

{| class="wikitable" style="margin: 1em auto 1em auto;" ! width="120" align="center"|Preceded by ! width="160" align="center"|Pole Star ! width="120" align="center"|Succeeded by |- |align="center"|'''Deneb''' |align="center"|~11,000 AD <br/>to<br/> ~11,500 AD |align="center"|'''Vega''' |}

== References == {{Reflist|refs=

<ref name=nsv>{{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=challouf2014>{{cite journal | display-authors=1 | last1=Challouf | first1=M. | last2=Nardetto | first2=N. | last3=Mourard | first3=D. | last4=Graczyk | first4=D. | last5=Aroui | first5=H. | last6=Chesneau | first6=O. | last7=Delaa | first7=O. | last8=Pietrzyński | first8=G. | last9=Gieren | first9=W. | last10=Ligi | first10=R. | last11=Meilland | first11=A. | last12=Perraut | first12=K. | last13=Tallon-Bosc | first13=I. | last14=McAlister | first14=H. | last15=Ten Brummelaar | first15=T. | last16=Sturmann | first16=J. | last17=Sturmann | first17=L. | last18=Turner | first18=N. | last19=Farrington | first19=C. | last20=Vargas | first20=N. | last21=Scott | first21=N. | title=Improving the surface brightness-color relation for early-type stars using optical interferometry⋆ | journal=Astronomy & Astrophysics | volume=570 | pages=A104 | year=2014 | arxiv=1409.1351 | doi=10.1051/0004-6361/201423772 | bibcode=2014A&A...570A.104C | s2cid=14624307 }}</ref>

<ref name=Anderson2012>{{cite journal | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | s2cid=119257644 }}</ref>

<ref name=aaa474_2_653>{{cite journal | 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 }}</ref>

<ref name=aass85_3_1015>{{cite journal | last1=Malagnini | first1=M. L. | last2=Morossi | first2=C. | title=Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars | journal=Astronomy and Astrophysics Supplement Series | volume=85 | issue=3 | pages=1015–1019 |date=November 1990 | bibcode=1990A&AS...85.1015M }}</ref>

<ref name=clpl4_99>{{cite journal | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | year=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name=rgcrv>{{cite journal | last=Evans | first=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | title=The Revision of the General Catalogue of Radial Velocities | volume=30 | pages=57 | journal=Determination of Radial Velocities and Their Applications, Proceedings from IAU Symposium No. 30 | bibcode=1967IAUS...30...57E }}</ref>

<ref name="gordon2019">{{cite journal |doi=10.3847/1538-4357/ab04b2 |title=Angular Sizes, Radii, and Effective Temperatures of B-type Stars from Optical Interferometry with the CHARA Array |year=2019 |last1=Gordon |first1=Kathryn D. |last2=Gies |first2=Douglas R. |last3=Schaefer |first3=Gail H. |last4=Huber |first4=Daniel |last5=Ireland |first5=Michael |journal=The Astrophysical Journal |volume=873 |issue=1 |page=91 |bibcode=2019ApJ...873...91G |s2cid=125181833 |doi-access=free }}</ref>

<ref name=aj81_245>{{cite journal | last1=Edwards | first1=T. W. | title=MK classification for visual binary components | journal=Astronomical Journal | volume=81 | pages=245–249 |date=April 1976 | doi=10.1086/111879 | bibcode=1976AJ.....81..245E }}</ref>

<ref name=malkov>{{cite journal | title=Dynamical masses of a selected sample of orbital binaries | last1=Malkov | first1=O. Yu. | last2=Tamazian | first2=V. S. | last3=Docobo | first3=J. A. | last4=Chulkov | first4=D. A. | display-authors=1 | journal=Astronomy & Astrophysics | volume=546 | id=A69 | pages=5 | date=October 2012 | doi=10.1051/0004-6361/201219774 | bibcode=2012A&A...546A..69M | doi-access=free }}</ref>

<ref name=bcd>{{cite journal | title=Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff | display-authors=1 | last1=Zorec | first1=J. | last2=Cidale | first2=L. | last3=Arias | first3=M. L. | last4=Frémat | first4=Y. | last5=Muratore | first5=M. F. | last6=Torres | first6=A. F. | last7=Martayan | first7=C. | journal=Astronomy and Astrophysics | volume=501 | issue=1 | pages=297–320 | date=July 2009 | arxiv=0903.5134 | bibcode=2009A&A...501..297Z | doi=10.1051/0004-6361/200811147 | s2cid=14969137 }}</ref>

<ref name=kalerAC>{{cite web | first1=James B. | last1=Kaler | work=Stars | publisher=University of Illinois | title=Delta Cygni | url=http://stars.astro.illinois.edu/sow/deltacyg.html | access-date=2018-10-03 }}</ref>

}}

{{Stars of Cygnus}}

Category:B-type giants Category:F-type main-sequence stars Category:K-type main-sequence stars Category:Triple star systems  Category:Cygnus (constellation) Cygni, Delta BD+44 3234 Cygni, 18 186882 097165 7528 Fawaris