20 Cygni
{{short description|Red giant star in the constellation Cygnus}}
{{Starbox begin
| name = 20 Cygni
}}
{{Starbox observe
| epoch = J2000
| constell = Cygnus
| dec = {{DEC|+52|59|16.7901}}
}}
{{Starbox character
| type =
| class = {{nowrap|K3 III CN2}}
| u-b =
| variable =
}}
{{Starbox astrometry
| radial_v = {{Val|−22.04|0.15}}
| parallax = 16.11
| p_error = 0.14
| absmag_v =
}}
{{Starbox detail
| source =
| temperature = {{Val|4337|67|fmt=commas}}
| age_gyr =
}}
{{Starbox catalog
| names = {{odlist | B=d Cyg | F=20 Cyg | BD=+52°2547 | FK5=3586 | HD=188056 | HIP=97635 | HR=7576 | SAO=32042 }}
}}
{{Starbox reference
| Simbad=20+Cyg
}}
{{Starbox end}}
20 Cygni is a single, orange-hued star in the northern constellation of Cygnus. It is a faint star but is visible to the naked eye with an apparent visual magnitude of 5.03. The distance to 20 Cygni can be estimated from its annual parallax shift of {{Val|16|ul=mas}}, which yields a range of 202 light years. It is moving closer to the Earth with a heliocentric radial velocity of {{Val|−22|u=km/s}}.
This is an aging red giant star with a stellar classification of {{nowrap|K3 III CN2}}, a star that has used up its core hydrogen and is expanding. The suffix notation indicates there are unusually strong lines of cyanogen in the spectrum. 20 Cyg is listed as one of the least variable stars in the Hipparcos catalogue, changing its brightness by no more than 0.01 magnitude. It has 1.28 times the mass of the Sun and has expanded to 13 times the Sun's radius. The star is radiating 57.5 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,337 K.
References
{{reflist|refs=
{{cite simbad | title=20 Cyg | access-date=2019-01-09 }}
{{Cite Gaia DR2|2048824680109512320}}
| last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C.
| title=The Perkins catalog of revised MK types for the cooler stars
| journal=Astrophysical Journal Supplement Series
| volume=71 | pages=245 | year=1989
| bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}
| 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
| display-authors=1 | 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 }}
| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.
| title=A catalogue of multiplicity among bright stellar systems
| journal=Monthly Notices of the Royal Astronomical Society
| volume=389 | issue=2 | pages=869–879 | date=September 2008
| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E
| arxiv=0806.2878 | s2cid=14878976 | postscript=. }}
| title=Abundances in the Local Region. I. G and K Giants
| last1=Luck | first1=R. Earle
| journal=Astronomical Journal | postscript=.
| volume=150 | issue=3 | at=88 | year=2015 | arxiv=1507.01466
| bibcode=2015AJ....150...88L | doi=10.1088/0004-6256/150/3/88 | s2cid=118505114 }}
| first=F. | last=van Leeuwen
| title=Validation of the new Hipparcos reduction
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664 | date=November 2007
| bibcode=2007A&A...474..653V | postscript=.
| doi=10.1051/0004-6361:20078357 | arxiv=0708.1752 | s2cid=18759600
}}
| last1=Adelman | first1=S. J.
| title=Research Note Hipparcos photometry: The least variable stars
| journal=Astronomy and Astrophysics
| volume=367 | pages=297–298 | year=2001 | postscript=.
| doi=10.1051/0004-6361:20000567 | bibcode=2001A&A...367..297A | doi-access=free }}
}}
{{Stars of Cygnus}}
Category:Cygnus (constellation)