Mu Draconis
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Mu Draconis (μ Draconis, abbreviated Mu Dra, μ Dra) is a multiple star system near the head of the constellation of Draco. With a combined magnitude of 4.92,<ref name=Simbad/> it is visible to the naked eye. Based on parallax estimates by the Hipparcos spacecraft, it is located approximately 89 light-years from the Sun.<ref name=HIP/>
The system consists of a single primary star (designated Mu Draconis A, officially named Alrakis Template:IPAc-en from the traditional name of the system),<ref name=Kunitzsch>Template:Cite book</ref><ref name="IAU-LSN">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> a secondary binary pair (Mu Draconis B) and a further single star (C). B's two components are designated Mu Draconis Ba and Bb.
Mu Draconis A and Ba are nearly identical F-type main-sequence stars, with masses of Template:Solar mass and Template:Solar mass, respectively.<ref name=tokovinin/> Both have the spectral class of F5V, and have similar apparent magnitude, at 5.66 and 5.69, respectively.<ref name=ORB6/> The secondary, Mu Draconis B, has a drifting radial velocity, and is itself a spectroscopic binary with an orbital period of 2,270 days.<ref name=SB9>Template:Cite journal (SB9 catalog entry)</ref> The distance between both stars is 2 arcseconds, so a telescope with a diameter of at least 6 centimetres is necessary to see them separate. The smaller component, Mu Draconis Bb, has a mass of Template:Solar mass. Mu Draconis C is a 14th magnitude common-proper-motion companion 13.2" away from the bright pair, with a mass of Template:Solar mass.<ref name=tokovinin/>
Nomenclature
μ Draconis (Latinised to Mu Draconis) is the star's Bayer designation. The designations of the three constituents as Mu Draconis A, B and C, and those of B's components - Mu Draconis Ba and Bb - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).<ref name="planetnaming">Template:Cite arXiv</ref>
It is also known by the name Arrakis (or Errakis), which is derived from the name given to it by Arabian stargazers, الراقص al-rāqiṣ "the trotting (camel)" (lit. "the dancing one").<ref name="k&s">Template:Cite book</ref><ref name="allen">Template:Cite book</ref>
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.<ref name="TriRpt18">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It approved the name Alrakis for the component Mu Draconis A on February 1, 2017, and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>
This star, along with Beta Draconis (Rastaban), Gamma Draconis (Eltanin), Nu Draconis ('Kuma') and Xi Draconis (Grumium) were Al ʽAwāïd, the Mother Camels, which were known in Latin as the Quinque Dromedarii.<ref>Template:Cite book</ref>
Cultural references
Science fiction writer Frank Herbert chose Arrakis as the name of the primary planet of Canopus (α Carinae) in his Dune series of novels, aware that the word "Arrakis" is the transliteration into English of the Arabic words for "the Dancer" (al-Raqis).<ref name="Palumbo2018">Template:Cite book</ref>