Gamma Draconis
Eltanin, γ Dra
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Location of γ Draconis (bottom left).
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Observation data
Epoch J2000 Equinox J2000 |
| Constellation |
Draco |
| Right ascension |
17h 56m 36.3699s[1] |
| Declination |
51° 29′ 20.022″[1] |
| Apparent magnitude (V) |
2.3617 [2] |
| Characteristics |
| Spectral type |
K5III [1] |
| U−B color index |
+1.87[3] |
| B−V color index |
+1.52 [3] |
| Astrometry |
|
| Radial velocity (Rv) |
-27.91 [1] km/s |
| Proper motion (μ) |
RA: -8.48 [2] mas/yr
Dec.: -22.79 [2] mas/yr |
| Parallax (π) |
21.14 ± 0.10[2] mas |
| Distance |
154.3 ± 0.7 ly
(47.3 ± 0.2 pc) |
| Absolute magnitude (MV) |
-1.01 [2] |
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| Details |
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| Mass |
1.7[4] M☉ |
| Radius |
50 [4] R☉ |
| Luminosity |
600 [4] L☉ |
| Temperature |
4,000 [4] K |
| Metallicity |
-0.14 Fe/H[5] |
| Rotational velocity (v sin i) |
<17[6] km/s |
|
| Other designations |
Etamin, Etanin, Ettanin, Rastaban, Rasaben, Zenith star, 33 Draconis, HR 6705, BD +51°2282, HD 164058, SAO 30653, FK5 676, HIP 87833. |
| Database references |
| SIMBAD |
data |
Coordinates: 17h 56m 36.37s, +51° 29′ 20.02″
Gamma Draconis (γ Dra, γ Draconis) is a star in the constellation Draco. It has the traditional name Etamin or Eltanin (Arabic: التنين At-Tinnin The great serpent), and the Flamsteed designation 33 Draconis.[1][4][7]
This star, along with β Dra (Rastaban), μ Dra (Erakis), ν Dra (Kuma) and ξ Dra (Grumium) were Al ʽAwāïd, "the Mother Camels", which was later known as the Quinque Dromedarii.[8]
In Chinese, 天棓 (Tiān Bàng), meaning Celestial Flail, refers to an asterism consisting of γ Draconis, ξ Draconis, ν Draconis, β Draconis and ι Herculis.[9] Consequently, γ Draconis itself is known as 天棓四 (Tiān Bàng sì, English: the Fourth Star of Celestial Flail.)[10]
Properties
Eltanin is an orange giant of spectral type K5, lying 148 light years away. Despite its Bayer designation of "gamma," it is actually the brightest star in Draco, outshining Rastaban (Beta Draconis) by nearly half a magnitude. In fact, the name "Rastaban" was formerly used for Eltanin, and the two terms share an Arabic root meaning "serpent" or "dragon." Its proximity to the point directly overhead of London has also earned it the name "Zenith Star." As for other places, it is relatively easy to locate in the night sky. If one finds Vega, Eltanin is the red star just north of it.
In 1.5 million years, Eltanin will pass within 28 light years of Earth. At this point (assuming its current absolute magnitude does not change) it will be the brightest star in the night sky, nearly as bright as Sirius is at present.
In 1728, while unsuccessfully attempting to measure the parallax of this star, James Bradley discovered the aberration of light resulting from the movement of the Earth. Bradley's discovery proved Copernicus' theory that the Earth revolved around the Sun.
Namesakes
USS Etamin (AK-93) was a United States Navy Crater class cargo ship named after the star.
See also
References
- ^ a b c d e "SIMBAD query result: NAME ETAMIN -- Star in double system". Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Gamma+Draconis&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id. Retrieved 2010-11-21.
- ^ a b c d e van Leeuwen, F (November 2007). asbg.fr/viz-bin/VizieR-S?HIP%2087833 "Hipparcos, the New Reduction". Astronomy and Astrophysics (Centre de Données astronomiques de Strasbourg) 474 (2): 653–664. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357. http://vizier.u-str asbg.fr/viz-bin/VizieR-S?HIP%2087833. Retrieved 2010-11-21.
- ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)" (PDF). Catalogue of Eggen's UBV data.. Bibcode 1986EgUBV........0M.
- ^ a b c d e Professor James B. (Jim) Kaler. "ELTANIN (Gamma Draconis).". University of Illinois. http://stars.astro.illinois.edu/sow/eltanin.html. Retrieved 2010-11-21.
- ^ McWilliam, Andrew (December 1990). "High-resolution spectroscopic survey of 671 GK giants" (PDF). Astrophysical Journal Supplement Series (ISSN 0067-0049), 74: p. 1075–1128. Bibcode 1990ApJS...74.1075M. doi:10.1086/191527.
- ^ "Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR. Centre de Données astronomiques de Strasbourg. http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HR%206705. Retrieved 2010-11-21.
- ^ "γ Dra (Eltanin)". Wikisky.org. http://www.server6.wikisky.org/starview?object_type=1&object_id=270&object_name=33+Dra. Retrieved 2010-11-22.
- ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 207. ISBN 0486210790. http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html. Retrieved 2010-12-12.
- ^ (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) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
External links
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| Bayer |
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| Flamsteed |
- 1 (λ, Gianfar)
- 2
- 3
- 4
- 5 (κ)
- 6
- 7
- 8
- 9
- 10 (i)
- 11 (α, Thuban)
- 12 (ι, Edasich)
- 13 (θ)
- 14 (η, Aldhibain)
- 15 (A)
- 16
- 17
- 18 (g)
- 19 (h)
- 20
- 21 (μ, Arrakis)
- 22 (ζ, Aldhibah)
- 23 (β, Rastaban)
- 24 (ν¹, Kuma)
- 25 (ν², Kuma)
- 26
- 27 (f)
- 28 (ω)
- 29
- 30
- 31 (ψ, Dziban)
- 32 (ξ, Grumium)
- 33 (γ, Eltanin)
- 34
- 35
- 36
- 37
- 38
- 39 (b)
- 40
- 41
- 42
- 43 (φ)
- 44 (χ)
- 45 (d)
- 46 (c)
- 47 (ο)
- 48
- 49
- 50
- 51
- 52 (υ)
- 53
- 54
- 55
- 56
- 57 (δ, Altais)
- 58 (π)
- 59
- 60 (τ)
- 61 (σ, Alsafi)
- 62
- 63 (ε, Tyl)
- 64 (e)
- 65
- 66
- 67 (ρ)
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
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