Delta Cygni

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Template:Short description

δ Cygni
Template:Location mark
Location of δ Cygni (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 2.87[2]
Characteristics
Spectral type A0 IV[3] (B9 III + F1 V[4])
U−B Template:Engvar −0.10[5]
B−V Template:Engvar −0.02[5]
Variable type Suspected[6]
Astrometry
Radial velocity (Rv)−20.1[7] km/s
Proper motion (μ) RA: +44.07[1] mas/yr
Dec.: +48.66[1] mas/yr
Parallax (π)19.77±0.48 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−0.74[8]
Orbit[9]
PrimaryA
CompanionB
Period (P)780.27 yr
Semi-major axis (a)3.0″
Eccentricity (e)0.4670
Details[10]
Mass2.93 Template:Solar mass
RadiusScript error: No such module "val".[11] Template:Solar radius
Luminosity155 Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[11] cgs
TemperatureScript error: No such module "val".[11] K
Rotational velocity (v sin i)142[11] km/s
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist
Database references
SIMBADdata

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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 Script error: No such module "convert". distant from the Sun.[1]

Delta Cygni's two components are designated Delta Cygni A (officially named Fawaris Template:IPAc-en)[12] 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.[13]

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).[14]

Traditionally, Delta Cygni had no proper name.[13] It belonged to the Arabic asterism al-Fawāris (Script error: No such module "Lang".), meaning "the Riders" in indigenous Arabic,[15] 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)[16] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[17] 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.[12]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), 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.[18] Consequently, the Chinese name for Delta Cygni itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[19] Script error: No such module "Labelled list hatnote".

Properties

The primary, Delta Cygni A, is a blue-white giant star of spectral class B9,[4] with a temperature of 10,400 K.[11] It is nearing the end of its main-sequence life stage with a luminosity 155 times that of the Sun,[10] a radius of 4.81 solar radii,[11] 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.[10]

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.[13]

The much more distant third companion is an orange (class K) twelfth magnitude star, and only two thirds as massive.[13]

The two main stars together appear with a spectral type of A0 IV.[3] As seen from Earth, the entire triple star system of Delta Cygni shines at a combined apparent magnitude of 2.87.[2] 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.[6]

Pole Star

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

Preceded by Pole Star Succeeded by
Deneb ~11,000 AD
to
~11,500 AD 		Vega

References

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  1. ↑ a b c d e f Script error: No such module "Citation/CS1".
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  3. ↑ a b Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "Citation/CS1".
  5. ↑ a b Script error: No such module "Citation/CS1".
  6. ↑ a b Script error: No such module "Citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ a b c Script error: No such module "Citation/CS1".
  11. ↑ a b c d e f Script error: No such module "Citation/CS1".
  12. ↑ a b Script error: No such module "citation/CS1".
  13. ↑ a b c d Script error: No such module "citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ 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.
  19. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 4 日 Template:Webarchive

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Template:Stars of Cygnus

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