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] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute magnitude (MV) | +0.74 ± 0.02[4] |
| Orbit[3] | |
| Primary | ε Cyg Aa |
| Companion | ε Cyg Ab |
| Period (P) | Script error: No such module "val". yr |
| Semi-major axis (a) | Script error: No such module "val". |
| Eccentricity (e) | Script error: No such module "val". |
| Argument of periastron (ω) (primary) | Script error: No such module "val".° |
| Semi-amplitude (K1) (primary) | 4.6 km/s |
| Details | |
| A | |
| Mass | Script error: No such module "val".[3] Template:Solar mass |
| Radius | 11.13[6] Template:Solar radius |
| Luminosity | Script error: No such module "val".[7] Template:Solar luminosity |
| Surface gravity (log g) | Script error: No such module "val".[7] cgs |
| Temperature | 4,699[6] K |
| Metallicity [Fe/H] | Script error: No such module "val".[6] dex |
| Rotation | Script error: No such module "val".[4] years |
| Rotational velocity (v sin i) | 2.3 ± 0.2[4] km/s |
| Age | Script error: No such module "val".[3] Gyr |
| B | |
| Mass | Script error: No such module "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 | |
| SIMBAD | data |
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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
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
- ↑ a b c d e Script error: No such module "citation/CS1". Note: see VizieR catalogue I/311.
- ↑ a b c Script error: No such module "citation/CS1".
- ↑ a b c d e f g h i j Script error: No such module "citation/CS1".
- ↑ a b c d Script error: No such module "Citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ a b c d e Script error: No such module "citation/CS1".
- ↑ a b c Script error: No such module "citation/CS1". Epsilon Cygni's database entry at VizieR.
- ↑ a b Script error: No such module "Citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ 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.
- ↑ 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.
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".