Template:Short description Template:About Template:Starbox begin Template:Starbox image Template:Starbox observe Template:Starbox character Template:Starbox astrometry Template:Starbox detail Template:Starbox catalog Template:Starbox reference Template:Starbox end
Mirach is a prominent star in the northern constellation of Andromeda. It is pronounced Template:IPAc-en<ref name=Kunitzsch/><ref name="IAU-CSN"/> and has the Bayer designation Beta Andromedae, which is Latinized from β Andromedae. This star is positioned northeast of the Great Square of Pegasus and is potentially visible to all observers north of latitude 54° S. It is commonly used by stargazers to find the Andromeda Galaxy. The galaxy NGC 404, also known as Mirach's Ghost, is seven arcminutes away from Mirach.<ref name=darling/>
This star has an apparent visual magnitude of around 2.07,<ref name=":1"/> varying between 2.01 and 2.10,<ref name=nsv/> which at times makes it the brightest star in the constellation. Based upon parallax measurements, it is roughly Template:Convert from the Sun.<ref name=aaa474_2_653/> Its apparent magnitude is reduced by 0.06 by extinction due to gas and dust along the line of sight.<ref name=aaa430_165/> The star has a negligible radial velocity of 0.1 km/s,<ref name=aaa430_165/> but with a relatively large proper motion, traversing the celestial sphere at an angular rate of Template:Val·yr−1.<ref name=Lepine2005/>
PropertiesEdit
Mirach is a single,<ref name=Eggleton_Tokovinin_2008/> aging red giant with a stellar classification of M0 III.<ref name=araa11_29/> It is currently on the asymptotic giant branch of its evolution.<ref name=Eggen1992/> The star has an estimated 2.49<ref name=Dehaes_et_al_2011/><ref name="Lee2023"/> times the mass of the Sun. Having exhausted the supply of hydrogen at its core, the outer envelope of the star has expanded to around 86 times the size of the Sun. It is radiating 1,675 times the luminosity of the Sun at an effective temperature of Template:Val.<ref name="Lee2023"/> Mirach is suspected of being a semiregular variable star, with an apparent visual magnitude varies from +2.01 to +2.10.<ref name=nsv/> Since 1943 the spectrum of this star has been one of the stable anchor points by which other stars are classified.<ref name=baas25_1319/> Template:Clear left
NomenclatureEdit
Beta Andromedae is the star's Bayer designation. It had the traditional name of Mirach, and its variations, such as Mirac, Mirar, Mirath, Mirak, etc. (the name is spelled Merach in Burritt's The Geography of the Heavens),<ref name=TGH/> which come from the star's description in the Alfonsine Tables of 1521 as super mizar. Here, mirat is a corruption of the Arabic مئزر mīzar "girdle", which appeared in a Latin translation of the Almagest.<ref name=allen/> This word refers to Mirach's position at the left hip of the princess Andromeda.<ref name=encarta/> In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name="WGSN1"/> included a table of the first two batches of names approved by the WGSN; which included Mirach for this star.
Mirach is listed in the Babylonian MUL.APIN as KA.MUSH.I.KU.E, meaning "the Deleter" (the alternative star is α Cas).<ref name=OAC/> Medieval astronomers writing in Arabic called Mirach Janb al-Musalsalah (Template:Langx); it was part of the 28th manzil (Arabian lunar mansion) Baṭn al-Ḥūt, the Belly of the Fish, or Qalb al-Ḥūt, the Heart of the Fish.<ref name=allen/><ref name=d-jr/> The star has also been called Cingulum and Ventrale.<ref name=allen/> This al-Ḥūt was an indigenous Arabic constellation, not the Western "Northern Fish" part of the constellation Pisces.<ref name=d-jr/> These names are not from the Arabic marāqq, loins, because it was never called al-Marāqq in Arabian astronomy.<ref name=d-jr/> Al Rishā', the Cord (of the well-bucket), on al-Sūfī's star map. It is origin of the proper name Alrescha for Alpha Piscium.<ref name=allen/><ref name=DMSN/>
In Chinese, {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}), meaning Legs, refers to an asterism consisting of Mirach (β Andromedae), η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, π Andromedae, ν Andromedae, μ Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ1 Piscium. Consequently, the Chinese name for β Andromedae itself is {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}, Template:Langx).<ref name=aeea/> Mirach was considered the standard "black" star; black could mean "dark red" in this context, especially in comparison to Antares, the standard red star.<ref>Template:Cite journal</ref>
The people of Micronesia named this star Kyyw, meaning "The Porpoise", and this was used as one of the names of the months in Micronesia.<ref name=EASASACA/>
Substellar companionEdit
A 2023 study detected radial velocity variations in Mirach (HD 6860), showing evidence of a substellar companion, likely a brown dwarf.<ref name="Lee2023"/>
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ReferencesEdit
Further readingEdit
- Davis Jr., G. A., (1971) Pronunciations, Derivations, and Meanings of a Selected List of Star Names, (rep.) Cambridge, Sky Publishing Corp.
- Kunitzsch, P., (1959) Arabische Sternnamen in Europa
- Kunitzsch. P., (ed.) (1990) Der Sternkatalog des Almagest, Band II