Pi1 Cygni
{{short description|Binary star system in the constellation Cygnus}}
{{DISPLAYTITLE:Pi1 Cygni}}
{{other stars by Bayer designation|Pi Cygni{{!}}π Cygni}}
{{Starbox begin
| name = Pi1 Cygni
}}
{{Starbox observe
| epoch = J2000.0
| constell = Cygnus
| dec = {{DEC|+51|11|22.6415}}
}}
{{Starbox character
| u-b =
| r-i =
| variable =
}}
{{Starbox astrometry
| radial_v =
| parallax = 1.89
| p_error = 0.15
}}
{{Starbox orbit
| period_unitless = 26.33 d
| eccentricity = 0.00
| periastron = {{nowrap|2431306.5 ± 10.0 JD}}
| periarg = 0.00
| k1 = 16.5
}}
{{Starbox detail
| source =
| component1 = π1 Cyg A
| temperature = {{Val|18360|1100|fmt=commas}}
| gravity =
| metal_fe =
}}
{{Starbox catalog
| names = π1 Cyg, 80 Cygni, BD+50°3410, FK5 3733, HD 206672, HIP 107136, HR 8301, SAO 33665.
}}
{{Starbox reference
| Simbad = pi.01+Cyg
}}
{{Starbox end}}
Pi1 Cygni (π1 Cygni, abbreviated Pi1 Cyg, π1 Cyg) is a binary star in the northern constellation of Cygnus. It is visible to the naked eye, having a combined apparent visual magnitude of 4.66. The distance to this system can be roughly gauged by its annual parallax shift of 1.89 mas, which yields a separation of around 1,700 light years from the Sun, give or take a hundred light years.
The two components are designated Pi1 Cygni A (officially named Azelfafage {{IPAc-en|@|'|z|E|l|f|@|f|ei|dZ}}, the traditional name for the system) and B.
Nomenclature
π1 Cygni (Latinised to Pi1 Cygni) is the star's Bayer designation. The designations of the two components as Pi1 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).{{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. }}
It bore the traditional name Azelfafage, derived from the Arabic ظلف الفرس Dhilf al-faras meaning "the horse track" or (probably) ذيل الدجاجة Dhail al-dajājah meaning "the tail of hen".p. 197, [https://books.google.com/books?id=5xQuAAAAIAAJ Star-names and Their Meanings], Richard Hinckley Allen, New York, G. E. Stechert, 1899. In 2016, the IAU organized a Working Group on Star Names (WGSN){{citation
| url=https://www.iau.org/science/scientific_bodies/working_groups/280/
| title=IAU Working Group on Star Names (WGSN)
| publisher=International Astronomical Union
| access-date=22 May 2016 | postscript=. }} to catalogue and standardize proper names for stars. The WGSN approved the name Azelfafage for Pi1 Cygni on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. For such names relating to members of multiple star systems, and where a component letter is not explicitly listed, the WGSN says that the name should be understood to be attributed to the brightest component by visual brightness{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin2.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 2 |access-date=16 December 2017}} - in this case Pi1 Cygni A.
In Chinese, {{lang|zh|螣蛇}} ({{lang|zh-Latn|Téng Shé}}), meaning Flying Serpent, refers to an asterism consisting of Pi1 Cygni, Alpha Lacertae, 4 Lacertae, Pi2 Cygni, HD 206267, Epsilon Cephei, Beta Lacertae, Sigma Cassiopeiae, Rho Cassiopeiae, Tau Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, Lambda Andromedae, Kappa Andromedae, Psi Andromedae and Iota Andromedae. Consequently, the Chinese name for Pi1 Cygni itself is {{lang|zh|螣蛇四}} ({{lang|zh-Latn|Téng Shé sì}}, {{langx|en|the Fourth Star of Flying Serpent}}){{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060707.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日] {{Webarchive|url=https://web.archive.org/web/20110521232711/http://aeea.nmns.edu.tw/2006/0607/ap060707.html |date=2011-05-21 }}
Properties
This is a single-lined spectroscopic binary with a close, circular orbit, having a period of just 26.33 days. The primary, component A, is a slightly evolved B-type subgiant star with a stellar classification of B3 IV. It has an estimated 10 times the mass of the Sun and around 5.6 times the Sun's radius. The star radiates 16,538 times the solar luminosity from its outer atmosphere at an effective temperature of roughly 18,360 K. It is about 25 million years old and is spinning with a projected rotational velocity of 55 km/s.
References
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| title=Naming Stars
|publisher=IAU.org
|access-date=16 December 2017}}
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| title=SB9: The ninth catalogue of spectroscopic binary orbits
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| postscript=. }}
| display-authors=1 | last1=Strom | first1=Stephen E.
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| title=B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?
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| title=A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
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| arxiv=1007.4883 | s2cid=118629873 | postscript=. }}
| title=pi.01 Cyg -- Spectroscopic binary
| work=SIMBAD Astronomical Database
| publisher=Centre de Données astronomiques de Strasbourg
| url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=pi01+Cyg
| access-date=2017-02-19 | postscript=. }}
}}
{{Stars of Cygnus|state=collapsed}}
Category:Spectroscopic binaries