Mu Draconis

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Mu Draconis
Draco constellation map.svg
Locator Dot.gif

The red dot shows the location of Mu Draconis in Draco.
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 17h 05m 19.7s
Declination +54° 28′ 13″
Apparent magnitude (V) 5.8 / 5.61
Spectral type F7V
U−B color index 0.05
B−V color index 0.48
Variable type -
Radial velocity (Rv) −4.5 km/s
Proper motion (μ) RA: −68.4 mas/yr
Dec.: 88.7 mas/yr
Parallax (π) 37.08 ± 0.89 mas
Distance 88 ± 2 ly
(27.0 ± 0.6 pc)
Absolute magnitude (MV) ?
Companion HIP 83608
Period (P) 672 yr
Semi-major axis (a) ?"
Eccentricity (e) ?
Inclination (i)
Longitude of the node (Ω)
Periastron epoch (T) ?
Other designations
Alrakis, 21 Draconis (21 Dra), HR 6370, BD +54°1857, HD 154906, SAO 30239, HIP 83608.

Mu Draconis (μ Draconis, μ Dra) is a binary star with a combined magnitude of 4.92m located approximately 85 light years from the Solar System, near the head of the constellation Draco. The component stars are nearly identical yellow-white stars in a tight 672 year orbit. Each is of the spectral class F7V and has a visual magnitude of 5.8m. Under ideal seeing conditions, the pair can be resolved with a small 60 mm (2.4 in) aperture telescope at about 120 power.

Mu Draconis is also known by its older name Alrakis,[1] [2] which is derived from name given to it in Arabic by Arabian stargazers, al-Rāqiṣ, "the Trotting Camel"[1][3] or "the Dancer."[2][3] This name is also sometimes spelled in the English as "Arrakis" or "Errakis".[3]

Older names[edit]

This star, along with β Dra (Rastaban), γ Dra (Eltanin), ν Dra (Kuma) and ξ Dra (Grumium) were Al ʽAwāïd, "the Mother Camels", which was later known as the Quinque Dromedarii.[4]

Cultural references[edit]

Science fiction writer Frank Herbert chose Arrakis as the name of the primary planet in his famous Dune series of novels, aware that the word "Arrakis" is the transliteration into English of the Arabic words for "the dancer" (al-Raqis). However, Herbert uses the name not to describe μ Draconis, but the fictional planet Arrakis as the third planet of the star Canopus (α Carinae) in the constellation Carina.


  1. ^ a b Kunitzsch, P.; Smart, T. (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, MA: Sky Pub. p. 35. ISBN 978-1-931559-44-7. 
  2. ^ a b Davis, Jr., G. A., (1971). Pronunciations, Derivations, and Meanings of a Selected List of Star Names (rep. ed.). Cambridge, MA: Sky Pub. Corp. p. 13. 
  3. ^ a b c Allen, R. H., (1963). Star Names: Their Lore and Meaning (rep. ed.). New York, NY: Dover Publications Inc. p. 211. ISBN 0-486-21079-0. 
  4. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 207. ISBN 0-486-21079-0. Retrieved 2010-12-12.