Epsilon Cygni

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Template:Short description

Epsilon Cygni
Template:Location mark
Location of ε Cyg (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 2.480[2]
Characteristics
Evolutionary stage Horizontal branch[3]
Spectral type K0 III[4]
U−B Template:Engvar +0.860[2]
B−V Template:Engvar +1.030[2]
Astrometry
Radial velocity (Rv)−12.41[5] km/s
Proper motion (μ) RA: 355.66[1] mas/yr
Dec.: 330.60[1] mas/yr
Parallax (π)44.86±0.12 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+0.74 ± 0.02[4]
Orbit[3]
Primaryε Cyg Aa
Companionε Cyg Ab
Period (P)Template:Val yr
Semi-major axis (a)Template:Val
Eccentricity (e)Template:Val
Argument of periastron (ω)
(primary)		Template:Val°
Semi-amplitude (K1)
(primary)		4.6 km/s
Details
A
MassTemplate:Val[3] Template:Solar mass
Radius11.13[6] Template:Solar radius
LuminosityTemplate:Val[7] Template:Solar luminosity
Surface gravity (log g)Template:Val[7] cgs
Temperature4,699[6] K
Metallicity [Fe/H]Template:Val[6] dex
RotationTemplate:Val[4] years
Rotational velocity (v sin i)2.3 ± 0.2[4] km/s
AgeTemplate:Val[3] Gyr
B
MassTemplate:Val[3] Template:Solar mass
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Aljanah, Gienah,[8] ε Cyg, 53 Cygni, BD+33°4018, FK5 780, GCTP 4959.00, Gl 806.1, HD 197989, HIP 102488, HR 7949, LHS 5358, SAO 70474, WDS 20462+3358[9]
Database references
SIMBADdata

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Epsilon Cygni (ε Cygni, abbreviated Epsilon Cyg, ε Cyg) is a binary star in the constellation of Cygnus. With an apparent visual magnitude of 2.48, it is readily visible to the naked eye at night, and is the third-brightest star in the constellation. Based upon parallax measurement, Epsilon Cygni is about 73 light-years distant.

The system has two confirmed constituents, Epsilon Cygni Aa (officially named Aljanah Template:IPAc-en) and Ab. Additionally, a visual companion (Epsilon Cygni C) is likely bound to the system.[3]

Nomenclature

ε Cygni (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 multiple star systems, and adopted by the International Astronomical Union (IAU).[10]

Epsilon Cygni bore the traditional name Gienah from the Arabic al janāħ (Template:Langx) meaning "the wing".[11] However that name was more usually applied to Gamma Corvi.[8] For reasons of disambiguation it was sometimes called Gienah Cygni. In 2016, the IAU organized a Working Group on Star Names (WGSN)[12] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[13] 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.[14]

In Chinese astronomy, the "Celestial Ford" (Template:Zh) refers to an asterism consisting of Epsilon Cygni, Gamma Cygni, Delta Cygni, 30 Cygni, Alpha Cygni, Nu Cygni, Tau Cygni, Upsilon Cygni and Zeta Cygni.[15] Consequently, the Chinese name for Epsilon Cygni Cygni itself is "the Ninth Star of Celestial Ford" (Template:Zh).[16]

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 arcseconds.[17] If the latter star is gravitationally bound to Epsilon Cygni A, then they are currently separated by 1,700 AU or more, and have an orbital period of at least 50,000 years.[18]

Properties

File:Cygnus 70 panel Mosaic in H-Alpha.jpg
ε Cygni appears north of the Veil nebula towards the bottom left

Epsilon Cygni A is a single-lined spectroscopic binary.[19] The components take 53 years to complete an orbit and are in a highly eccentric orbit, which put their distances from 1.1 astronomical units in apoapsis to 30.5 astronomical units in periapsis.[3]Template:Efn Its main component is a giant star with a stellar classification of K0 III.[20] 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 core.[3] The effective temperature of its photosphere is 4,700 K,[6] giving an orange hue that is a characteristic of K-type stars.[21] Being 10% more massive than the Sun and nine billion years old,[3] It has 11 times the radius of the Sun[6] and is about 56 times more luminous.[7]

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 Template:Solar mass.[3]

Since 1943, the spectrum of Epsilon Cygni A has served as one of the stable anchor points by which other stars are classified.[22]

Veil Nebula

Script error: No such module "Labelled list hatnote". 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

Template:Reflist

External links

Template:Stars of Cygnus

  1. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named aaa474_2_653
  2. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named aaass65_2_405
  3. ↑ a b c d e f g h i j Cite error: Invalid <ref> tag; no text was provided for refs named Heeren2021
  4. ↑ a b c d Script error: No such module "Citation/CS1".
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aj135_1_209
  6. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named Gray2019
  7. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named da Silva
  8. ↑ a b Script error: No such module "Citation/CS1".
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named hinkley1899
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named IAU-LSN
  15. ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  16. ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named pasp104_682_1173
  18. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named kaler
  19. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named WDS
  20. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aj117_4_1864
  21. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named csiro
  22. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named baas25_1319
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