Beta Draconis

Beta Draconis (β Draconis, abbreviated Beta Dra, β Dra) is a binary star and the third-brightest star in the northern circumpolar constellation of Draco. With an apparent visual magnitude of 2.79,[2] it is bright enough to be easily seen with the naked eye. Based upon parallax measurements from the Hipparcos astrometry satellite,[11][12] it lies at a distance of about 380 light-years (120 parsecs) from the Sun.[1]

β Draconis
Draco constellation map.svg
Red circle.svg
Location of β Draconis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 17h 30m 25.96170s[1]
Declination +52° 18′ 04.9993″[1]
Apparent magnitude (V) 2.79[2]
Spectral type G2Ib-IIa[3]
U−B color index +0.64[4]
B−V color index +0.98[4]
R−I color index +0.48[4]
Radial velocity (Rv)−20.0 ± 0.9[5] km/s
Proper motion (μ) RA: −15.89[1] mas/yr
Dec.: +12.28[1] mas/yr
Parallax (π)8.58 ± 0.10[1] mas
Distance380 ± 4 ly
(117 ± 1 pc)
Absolute magnitude (MV)–2.28[6]
Mass6.0 ± 0.2[2] M
Radius40[7] R
Luminosity1,000[8] L
Surface gravity (log g)1.86 ± 0.04[2] cgs
Temperature5,160 ± 150[2] K
Rotational velocity (v sin i)13[4] km/s
Age65[2] Myr
Other designations
Rastaban, Rastaben, NGCA-V25,[9] Alwaid, Asuia, β Dra, Beta Draconis, 23 Draconis, 23 Dra, BD+52 2065, FK5 653, HD 159181, HIP 85670, HR 6536, SAO 30429, ADS 10611, WDS 17304+5218A[5][4][10]
Database references

The two components are designated Beta Draconis A (officially named Rastaban /ˈræstəbæn/, the traditional name of the system)[13] and B.

The star was confirmed as a variable star with a range of about 1/100th of a magnitude by Gabriel Cristian Neagu using data from the TESS and Hipparcos missions.[14][15] The variability was reported to the AAVSO (American Association of Variable Star Observers), in the Variable Star Index.[16]


β Draconis (Latinised to Beta Draconis) is the system's Bayer designation. The designations of the two components as Beta Draconis 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).[17]

It bore the traditional name Rastaban, which has also been used for Gamma Draconis.[7][18] 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 /ælˈwd/,[19] the latter from the Arabic al-ʽawāʼidh "the old mother camels".[19] In 2016, the IAU organized a Working Group on Star Names (WGSN)[20] to catalogue and standardize proper names for stars. The WGSN approved the name Rastaban for the component Beta Draconis A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[13]

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.[18]

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.[21] Consequently, the Chinese name for Beta Draconis itself is known as 天棓三 (Tiān Bàng sān, English: the Third Star of Celestial Flail).[18][22][23]

The binary system consists of a bright giant orbited by a dwarf companion once every four millennia or so.[5][7]

Compared to the Sun, Beta Draconis A is an enormous star with six times the mass and roughly 40 times the radius. At this size, it is emitting about 950 times the luminosity of the Sun from its outer envelope at an effective temperature of 5,160 K,[2] giving it the yellow hue of a G-type star.[24] The spectrum matches a stellar classification of G2 II,[2] with the luminosity class of II indicating it is a bright giant. It is about 67 million years old.[2]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600
  2. ^ a b c d e f g h i 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, arXiv:0911.1335, Bibcode:2010MNRAS.402.1369L, doi:10.1111/j.1365-2966.2009.15979.x, S2CID 119096173
  3. ^ Keenan, P. C.; Pitts, R. E. (1980), "Revised MK spectral types for G, K ANS M stars", The Astrophysical Journal Supplement Series, 42: 541, Bibcode:1980ApJS...42..541K, doi:10.1086/190662
  4. ^ a b c d e 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.
  5. ^ a b c * bet Dra -- Star in double system, database entry, SIMBAD. Accessed on line September 17, 2008.
  6. ^ 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
  7. ^ a b c Rastaban Archived December 10, 2008, at the Wayback Machine, Stars, Jim Kaler. Accessed on line September 17, 2008.
  8. ^ Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M
  9. ^
  10. ^ 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.
  11. ^ 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
  12. ^ Perryman, Michael (2010), "The Making of History's Greatest Star Map", The Making of History's Greatest Star Map, Astronomers’ Universe, Heidelberg: Springer-Verlag,, doi:10.1007/978-3-642-11602-5, ISBN 978-3-642-11601-8
  13. ^ a b Naming Stars,, retrieved 2 March 2018
  14. ^ Ricker, George R.; Winn, Joshua N.; Vanderspek, Roland; Latham, David W.; Bakos, Gáspár. Á.; Bean, Jacob L.; Berta-Thompson, Zachory K.; Brown, Timothy M.; Buchhave, Lars; Butler, Nathaniel R.; Butler, R. Paul; Chaplin, William J.; Charbonneau, David; Christensen-Dalsgaard, Jørgen; Clampin, Mark; Deming, Drake; Doty, John; De Lee, Nathan; Dressing, Courtney; Dunham, E. W.; Endl, Michael; Fressin, Francois; Ge, Jian; Henning, Thomas; Holman, Matthew J.; Howard, Andrew W.; Ida, Shigeru; Jenkins, Jon; Jernigan, Garrett; et al. (2014), Oschmann, Jacobus M; Clampin, Mark; Fazio, Giovanni G; MacEwen, Howard A (eds.), "Transiting Exoplanet Survey Satellite (TESS)", Space Telescopes and Instrumentation 2014: Optical, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, 9143: 914320, arXiv:1406.0151, Bibcode:2014SPIE.9143E..20R, doi:10.1117/12.2063489, hdl:1721.1/97916, S2CID 54001919
  15. ^ ESA (1997), "The HIPPARCOS and TYCHO catalogues. Astrometric and photometric star catalogues derived from the ESA HIPPARCOS Space Astrometry Mission", Esa Special Publication, 1200, Bibcode:1997ESASP1200.....E
  16. ^
  17. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  18. ^ a b c 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
  19. ^ a b Kunitzsch, Paul; Smart, Tim (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.), Cambridge, Massachusetts: Sky Pub, ISBN 978-1-931559-44-7
  20. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016
  21. ^ (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.
  22. ^ (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.
  23. ^ Alwaid, Constellations of Words, Anne Wright. Accessed on line September 17, 2008.
  24. ^ "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

External linksEdit

  • Dibon-Smith, Richard (1992). StarList 2000: A Quick Reference Star Catalog for Astronomers. New York: John Wiley & Sons. ISBN 0-471-55895-8