Mu Draconis (μ Draconis, abbreviated Mu Dra, μ Dra) is a

multiple star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speaki ...

near the head of the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Draco Draco is the Latin word for serpent or dragon. Draco or Drako may also refer to: People * Draco (lawgiver) (from Greek: Δράκων; 7th century BC), the first lawgiver of ancient Athens, Greece, from whom the term ''draconian'' is derived * ...

. With a combined

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of 4.92, it is visible to the naked eye. Based on

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

estimates by the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

spacecraft, it is located approximately 89

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. The system consists of a single primary star (designated Mu Draconis A, officially named Alrakis from the traditional name of the system), 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 star An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII ...

s, with masses of and , respectively. Both have the

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

of F5V, and have similar

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

, at 5.66 and 5.69, respectively. The secondary, Mu Draconis B, has a drifting radial velocity, and is itself a

spectroscopic binary A binary star is a system of two star, stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separa ...

with an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 2,270 days.
SB9 catalog entry
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 . Mu Draconis C is a 14th magnitude common-proper-motion companion 13.2" away from the bright pair, with a mass of .

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

s, and adopted by the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

(IAU). 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"). In 2016, the

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. 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. This star, along with

Beta Draconis Beta Draconis, a name Latinized from β Draconis, is a binary star system and the third-brightest star in the northern circumpolar constellation of Draco. The two components are designated Beta Draconis A (officially named Rastaban , ...

(Rastaban),

Gamma Draconis Gamma Draconis (γ Draconis, abbreviated Gamma Dra, γ Dra), formally named Eltanin , is a star in the northern constellation of Draco. Contrary to its gamma-designation (historically third-ranked), it is the brightest star in Draco at ...

(Eltanin),

Nu Draconis Nu Draconis (also known as ν Dra, ν Draconis, or traditionally as Kuma ) is a double star in the constellation Draco. The respective components are designated ν1 Draconis and ν2 Draconis. The second component is a spectroscopic bin ...

('Kuma') and

Xi Draconis Xi Draconis (ξ Draconis, abbreviated Xi Dra, ξ Dra) is a double or binary star in the northern circumpolar constellation of Draco. It has an apparent visual magnitude of 3.75. Based upon parallax measurements, it is located at a dis ...

(Grumium) were ''Al ʽAwāïd'', the Mother Camels, which were known in Latin as the Quinque Dromedarii.

Cultural references

Science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel unive ...

writer

Frank Herbert Franklin Patrick Herbert Jr. (October 8, 1920February 11, 1986) was an American science fiction author best known for the 1965 novel '' Dune'' and its five sequels. Though he became famous for his novels, he also wrote short stories and worked a ...

chose

Arrakis Arrakis ()—informally known as Dune and later called Rakis—is a fictional desert planet featured in the ''Dune'' series of novels by Frank Herbert. Herbert's first novel in the series, 1965's ''Dune'', is considered one of the greatest scien ...

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).

References

{{DEFAULTSORT:Mu Draconis Binary stars Draco (constellation) Draconis, Mu Draconis, 21 F-type main-sequence stars Alrakis 083608 6369 70 Durchmusterung objects 154905 6 9584