- Delta Cygni
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Delta Cygni Observation data
Epoch J2000 Equinox J2000Constellation Cygnus Right ascension 19h 44m 58.5s Declination +45° 7′ 51″ Apparent magnitude (V) 2.86 Characteristics Spectral type B9.5IV+F1V U−B color index 0.49 B−V color index 0.582 Variable type no Astrometry Proper motion (μ) RA: 0.053 mas/yr
Dec.: 0.047 mas/yrParallax (π) 19.07 ± 0.45 mas Distance 171 ± 4 ly
(52 ± 1 pc)Absolute magnitude (MV) -0.74 Details Mass 3.15 M☉ Radius 4.7 R☉ Luminosity 180 L☉ Temperature 9,800 K Metallicity ? Rotation 135 km/s. Age ? years Other designations Delta Cygni (δ Cygni, δ Cyg) is the third-magnitude star in the constellation Cygnus. It has the traditional name Rukh. It will be the "North Star" for at least four centuries around 11,250.
This star belonged to the arabic asterism al-Fawāris (الفوارس), meaning "the Riders" in indigenous Arabic.[1], together with ζ, ε, and γ Cyg, the transverse of the Northern Cross.
In Chinese, 天津 (Tiān Jīn), meaning Celestial Ford, refers to an asterism consisting of δ Cygni, γ Cygni, 30 Cygni, α Cygni, ν Cygni, τ Cygni, υ Cygni, ζ Cygni and ε Cygni.[2] Consequently, δ Cygni itself is known as 天津二 (Tiān Jīn èr, English: the Second Star of Celestial Ford.)[3]
Contents
Features
Delta Cygni is a triple star; the system lies at a distance of about 170 light years and consists of two stars quite close together and one much farther out. This sort of common configuration lends stability.
The bright naked-eye star is a blue-white subgiant of spectral class B9.5, with a temperature of 9,800 kelvins. It is nearing the end of its main-sequence life stage with a luminosity 180 times that of the Sun, a radius of 4.7 solar radii, and a mass approximately 3.15 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. Its close companion is a yellow-white class F of the sixth magnitude (6.33) with a luminosity about 6 times that of the sun, and a mass about 1.5 times that of the sun. The much more distant third companion is an orange (class K) twelfth magnitude star, being only 38% as luminous as the sun, and only 70% as massive as the sun. As seen from Earth, the entire triple star system of Delta Cygni shines at a combined apparent magnitude of 2.86.
'North star'
It is one of eight bright stars in the northern hemisphere that lay claim to the position of "North Star" over the course of Earth's 26,000-year precession cycle.
The other seven stars are
- Tau Herculis (of Hercules),
- Vega (of Lyra),
- Alpha Cephei (of Cepheus),
- Gamma Cephei (of Cepheus),
- Polaris (of Ursa Minor),
- Kappa Draconis (of Draco), and
- Alpha Draconis (of Draco).
See also
References
- ^ Allen, R. H., (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc.. pp. 193, 197. ISBN 0486210790.
- ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 9789867332257.
- ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 4 日
External links
- Marshall "Roc" Burns, My Nickname: The Mythological Roc - TheRoc.net
- James B. "Jim" Kaler, DELTA CYG (Delta Cygni) - STARS
- Alan M. MacRobert, Understanding Celestial Coordinates - Sky & Telescope
- Richard Powell, The Brightest Stars - An Atlas of The Universe
Bayer Flamsteed 1 (κ) • 2 • 4 • 6 (β, Albireo) • 7 (ι¹) • 8 • 9 • 10 (ι²) • 11 • 12 (φ) • 13 (θ) • 14 • 15 • 16 (c) • 17 • 18 (δ, Rukh) • 19 • 20 (d) • 21 (η) • 22 • 23 • 24 (ψ) • 25 • 26 (e) • 27 (b¹) • 28 (b²) • 29 (b³) • 30 • 31 (ο¹) • 32 (ο²) • 33 • 34 (P) • 35 • 36 • 37 (γ, Sadr) • 39 • 40 • 41 • 42 • 43 • 44 • 45 (ω¹) • 46 (ω²) • 47 • 48 • 49 • 50 (α, Deneb) • 51 • 52 • 53 (ε, Gienah) • 54 (λ) • 55 • 56 • 57 • 58 (ν) • 59 (f¹) • 60 • 61 • 62 (ξ) • 63 (f²) • 64 (ζ) • 65 (τ) • 66 (υ) • 67 (σ) • 68 (A) • 69 • 70 • 71 (g) • 72 • 73 (ρ) • 74 • 75 • 76 • 77 • 78 (μ) • 79 • 80 (π¹, Azelfafage) • 81 (π², Pennae Caudalis)Nearby Other List Categories:- Bayer objects
- Cygnus constellation
- B-type subgiants
- F-type main sequence stars
- K-type main sequence stars
- Triple star systems
- Star stubs
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