Mu Aurigae is a candidate

binary star A binary star or binary star system is a system of two stars that are 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 as separate stars us ...

system in the

northern Northern may refer to the following: Geography * North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating ...

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 first constellati ...

Auriga Auriga is a constellation in the northern celestial hemisphere. It is one of the 88 modern constellations; it was among the 48 constellations listed by the 2nd-century astronomer Ptolemy. Its name is Latin for '(the) charioteer', associating i ...

. Its name is a

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

that is Latinized from μ Aurigae, and abbreviated Mu Aur or μ Aur. This star is visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

with an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...

of +4.88. Based upon an annual

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

shift of as seen from Earth, it is located approximately 162

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s from the Sun. This system is drifting further away with a

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

of +26 km/s. This is an

A-type main-sequence star An A-type main-sequence star (A) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

with a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...

of A4 Vm; the 'm' suffix indicating that abnormal abundances of heavier elements appear in the star's

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

, making this an

Am star An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. ...

. It is 560

million years Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used ...

old with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bu ...

of . This star has 1.90 the

mass of the Sun The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies a ...

and 2.5 times the Sun's radius. It is radiating 23 times the

Sun's luminosity The solar luminosity () is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal s ...

from its

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

at an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 7,931 K. A very close companion has been reported using

speckle interferometry Speckle imaging comprises a range of high-resolution Astrophotography, astronomical imaging techniques based on the analysis of large numbers of short Exposure (photography), exposures that freeze the variation of Astronomical seeing, atmospheri ...

, but this remains unconfirmed. The separation at discovery in 1986 was and it was measured at in 1999. It was catalogued by ''

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 and distances of ...

'' as a problem binary, indicating that the measurements of its position were not consistent with the motion of a single star, and no satisfactory orbit could be found to match the motion.

Name

This star, along with λ Aur and σ Aur, were Kazwini's ''Al Ḣibāʽ'' (ألحباع), the Tent. According to the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Al Ḣibāʽ'' were the title for three stars: λ Aur as ''Al Ḣibāʽ I'', μ Aur as ''Al Ḣibāʽ II'' and σ Aur as ''Al Ḣibāʽ III''. In

Chinese Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...

, (), meaning '' Celestial Pier'', refers to an asterism consisting of μ Aurigae, 19 Aurigae, φ Aurigae, 14 Aurigae and σ Aurigae. Consequently, μ Aurigae itself is known as (, ).AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 13 日

References

External links

HR 1689

Image Mu Aurigae
{{DEFAULTSORT:Mu Aurigae A-type main-sequence stars Am stars Binary stars Auriga Aurigae, Mu

1689 Events Notable events during this year include: * Coup, war, and legislation in England and its territories. ** The overthrow of Catholic king James of England, Ireland, and Scotland in the Glorious Revolution. ** The latter realms ente ...

BD+38 1063 Aurigae, 11 033641 024340