Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||17h 30m 25.96170s|
|Declination||+52° 18′ 04.9993″|
|Apparent magnitude (V)||2.79|
|Spectral type||G2 II|
|U−B color index||+0.64|
|B−V color index||+0.98|
|R−I color index||+0.48|
|Radial velocity (Rv)||−20.0 ± 0.9 km/s|
|Proper motion (μ)||RA: −15.89 mas/yr
Dec.: +12.28 mas/yr
|Parallax (π)||8.58 ± 0.10 mas|
|Distance||380 ± 4 ly
(117 ± 1 pc)
|Absolute magnitude (MV)||–2.28|
|Mass||6.0 ± 0.2 M☉|
|Surface gravity (log g)||1.86 ± 0.04 cgs|
|Temperature||5,160 ± 150 K|
|Rotational velocity (v sin i)||13 km/s|
Beta Draconis (β Draconis, abbreviated Beta Dra, β Dra), also named Rastaban, is a binary star and the third-brightest star in the northern circumpolar constellation of Draco. With an apparent visual magnitude of 2.79, it is bright enough to be easily seen with the naked eye. Based upon parallax measurements from the Hipparcos astrometry satellite, it lies at a distance of about 380 light-years (120 parsecs) from the Sun.
It bore the traditional name Rastaban, which has also been used for Gamma Draconis. This name, less commonly written Rastaben, derives from the Arabic phrase ra's ath-thu'ban "head of the serpent/dragon". It was also known as Asuia and Alwaid, the latter meaning "who is to be destroyed," though some trace it to Arabic al'awwad "the lute player". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Rastaban for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Beta Draconis is part of the asterism of the Mother Camels (Arabic al'awa'id), along with Gamma Draconis (Eltanin), Mu Draconis (Erakis), Nu Draconis (Kuma) and Xi Draconis (Grumium), which was later known as the Quinque Dromedarii.
In Chinese, 天棓 (Tiān Bàng), meaning Celestial Flail, refers to an asterism consisting of Beta Draconis, Xi Draconis, Nu Draconis, Gamma Draconis and Iota Herculis. Consequently, Beta Draconis itself is known as 天棓三 (Tiān Bàng sān, English: the Third Star of Celestial Flail.)
Compared to the Sun, this is an enormous star with six times the mass and roughly 40 times the radius. At this size, Beta Draconis is emitting about 950 times the luminosity of the Sun from its outer envelope at an effective temperature of 5,160 K, giving it the yellow hue of a G-type star. The spectrum matches a stellar classification of G2 II, with the luminosity class of II indicating it is a bright giant. It is about 67 million years old.
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv: , doi:10.1051/0004-6361:20078357
- Lyubimkov, Leonid S.; et al. (February 2010), "Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 402 (2): 1369–1379, Bibcode:2010MNRAS.402.1369L, arXiv: , doi:10.1111/j.1365-2966.2009.15979.x
- Molenda-Żakowicz, J.; Sousa, S. G.; Frasca, A.; Uytterhoeven, K.; Briquet, M.; Van Winckel, H.; Drobek, D.; Niemczura, E.; Lampens, P.; Lykke, J.; Bloemen, S.; Gameiro, J. F.; Jean, C.; Volpi, D.; Gorlova, N.; Mortier, A.; Tsantaki, M.; Raskin, G. (2013). "Atmospheric parameters of 169 F-, G-, K- and M-type stars in the Kepler field". Monthly Notices of the Royal Astronomical Society. 434 (2): 1422. Bibcode:2013MNRAS.434.1422M. arXiv: . doi:10.1093/mnras/stt1095.
- HR 6536, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 17, 2008.
- * bet Dra -- Star in double system, database entry, SIMBAD. Accessed on line September 17, 2008.
- Elgarøy, Øystein; Engvold, Oddbjørn; Lund, Niels (March 1999), "The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity", Astronomy and Astrophysics, 343: 222–228, Bibcode:1999A&A...343..222E
- Rastaban Archived December 10, 2008, at the Wayback Machine., Stars, Jim Kaler. Accessed on line September 17, 2008.
- Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M
- Entry 17304+5218, The Washington Double Star Catalog Archived 2008-04-13 at the Wayback Machine., United States Naval Observatory. Accessed on line September 17, 2008.
- "IAU Catalog of Star Names". Retrieved 28 July 2016.
- Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; et al. (July 1997), "The Hipparcos Catalogue", Astronomy and Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P
- Perryman, Michael (2010), "The Making of History's Greatest Star Map", The Making of History's Greatest Star Map:, Astronomers’ Universe, Heidelberg: Springer-Verlag, Bibcode:2010mhgs.book.....P, ISBN 978-3-642-11601-8, doi:10.1007/978-3-642-11602-5
- Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. pp. 207–208. ISBN 0-486-21079-0. Retrieved 2010-12-12.
- IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
- (in 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 978-986-7332-25-7.
- (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.
- Alwaid, Constellations of Words, Anne Wright. Accessed on line September 17, 2008.
- "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16