Astronomy:Mirach

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Mirach is a prominent star in the northern constellation of Andromeda. It is pronounced /ˈmaɪræk/[1][2] 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.[3]

This star has an apparent visual magnitude of around 2.07,[4] varying between 2.01 and 2.10,[5] which at times makes it the brightest star in the constellation. Based upon parallax measurements, it is roughly 197 light-years (60 parsecs) from the Solar System.[6] Its apparent magnitude is reduced by 0.06 by extinction due to gas and dust along the line of sight.[7] The star has a negligible radial velocity of 0.1 km/s,[7] but with a relatively large proper motion, traversing the celestial sphere at an angular rate of 0.208″·yr−1.[8]

Properties

A light curve for Mirach, plotted from Hipparcos data[9]

Mirach is a single,[10] aging red giant with a stellar classification of M0 III.[11] It is currently on the asymptotic giant branch of its evolution.[12] The star has an estimated 2.49 times the mass of the Sun.[13] 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[14] at an effective temperature of 3,762 K.[15] Mirach is suspected of being a semiregular variable star, with an apparent visual magnitude varies from +2.01 to +2.10.[5] Since 1943 the spectrum of this star has been one of the stable anchor points by which other stars are classified.[16]

Nomenclature

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),[17] 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.[18] This word refers to Mirach's position at the left hip of the princess Andromeda.[19] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[20] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[21] 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).[22] Medieval astronomers writing in Arabic called Mirach Janb al-Musalsalah (English: The Side of the Chained (Lady)); 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.[18][23] The star has also been called Cingulum and Ventrale.[18] This al-Ḥūt was an indigenous Arabic constellation, not the Western "Northern Fish" part of the constellation Pisces.[23] These names are not from the Arabic marāqq, loins, because it was never called al-Marāqq in Arabian astronomy.[23] Al Rishā', the Cord (of the well-bucket), on al-Sūfī's star map. It is the origin of the proper name Alrescha for Alpha Piscium.[18][24]

In Chinese, 奎宿 (Kuí Sù), 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 奎宿九 (Kuí Sù jiǔ, English: the Ninth Star of Legs).[25] Mirach was considered the standard "black" star; black could mean "dark red" in this context, especially in comparison to Antares, the standard red star.[26]

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.[27]

Substellar companion

A 2023 study detected radial velocity variations in Mirach (HD 6860), showing evidence of a substellar companion, likely a brown dwarf.[28]

The Mirach planetary system[28]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥28.26+2.05
−2.17 MJ 		2.03±0.01 663.87+4.61
−4.31 		0.28+0.10
−0.09 		— —

References

  1. ↑ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7. 
  2. ↑ "IAU Catalog of Star Names". http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt. 
  3. ↑ Darling, David. "Mirach's Ghost (NGC 404)". The Internet Encyclopedia of Science. http://www.daviddarling.info/encyclopedia/M/Mirachs_Ghost.html. Retrieved 2008-08-15. 
  4. ↑ "HD 6860 Overview". NASA Exoplanet Archive. https://exoplanetarchive.ipac.caltech.edu/overview/HD%206860. 
  5. ↑ 5.0 5.1 Samus, N. N.; Durlevich, O. V.; Al, Et (November 2004). "VizieR Online Data Catalog: Combined General Catalogue of Variable Stars (Samus+ 2004)" (in en). VizieR Online Data Catalog 2250: II/250. Bibcode: 2004yCat.2250....0S.  Mirach's database entry at VizieR.
  6. ↑ van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. 
  7. ↑ 7.0 7.1 Famaey, B. et al. (January 2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics 430 (1): 165–186. doi:10.1051/0004-6361:20041272. Bibcode: 2005A&A...430..165F. 
  8. ↑ Lépine, Sébastien; Shara, Michael M. (March 2005). "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)". The Astronomical Journal 129 (3): 1483–1522. doi:10.1086/427854. Bibcode: 2005AJ....129.1483L. 
  9. ↑ "/ftp/cats/more/HIP/cdroms/cats". Strasbourg astronomical Data Center. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats. 
  10. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society 389 (2): 869–879. doi:10.1111/j.1365-2966.2008.13596.x. Bibcode: 2008MNRAS.389..869E. 
  11. ↑ Morgan, W. W.; Keenan, P. C. (1973). "Spectral Classification". Annual Review of Astronomy and Astrophysics 11 (1): 29. doi:10.1146/annurev.aa.11.090173.000333. Bibcode: 1973ARA&A..11...29M. 
  12. ↑ Eggen, Olin J. (July 1992). "Asymptotic giant branch stars near the sun". Astronomical Journal 104 (1): 275–313. doi:10.1086/116239. Bibcode: 1992AJ....104..275E. 
  13. ↑ Dehaes, S. et al. (September 2011). "Structure of the outer layers of cool standard stars". Astronomy & Astrophysics 533: A107. doi:10.1051/0004-6361/200912442. Bibcode: 2011A&A...533A.107D. 
  14. ↑ McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017-10-01). "Fundamental parameters and infrared excesses of Tycho-Gaia stars". Monthly Notices of the Royal Astronomical Society 471: 770–791. doi:10.1093/mnras/stx1433. ISSN 0035-8711. Bibcode: 2017MNRAS.471..770M. 
  15. ↑ Dencs, Z.; Derekas, A.; Mitnyan, T.; Andersen, M. F.; Cseh, B.; Grundahl, F.; Hegedűs, V.; Kovács, J. et al. (May 2024). "Atmospheric Parameters and Abundances of Cool Red Giant Stars" (in en). Publications of the Astronomical Society of the Pacific 136 (5): 054202. doi:10.1088/1538-3873/ad4177. ISSN 1538-3873. 
  16. ↑ Garrison, R. F. (December 1993). "Anchor Points for the MK System of Spectral Classification". Bulletin of the American Astronomical Society 25: 1319. Bibcode: 1993AAS...183.1710G. http://www.astro.utoronto.ca/~garrison/mkstds.html. Retrieved 2012-02-04. 
  17. ↑ Burritt, Elijah Hinsdale; Mattison, Hiram; Whitall, Henry (1856). The Geography of the Heavens. New York: Sheldon & Company. p. 18. https://archive.org/details/geographyheaven01mattgoog. Retrieved 2025-03-21. 
  18. ↑ 18.0 18.1 18.2 18.3 Allen, R. A. (1899). Star-names and Their Meanings. p. 36. https://books.google.com/books?id=5xQuAAAAIAAJ. 
  19. ↑ Mirach, MSN Encarta. Accessed on line August 19, 2008. Archived 2009-10-31.
  20. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  21. ↑ "Bulletin of the IAU Working Group on Star Names, No. 1". http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf. 
  22. ↑ Rogers, J. H. (February 1998). "Origins of the ancient constellations: I. The Mesopotamian traditions". Journal of the British Astronomical Association 108 (1): 9–28. Bibcode: 1998JBAA..108....9R. 
  23. ↑ 23.0 23.1 23.2 Davis Jr., George A. (1971). Selected List of Star Names. p. 5. 
  24. ↑ Kunitsch, Paul; Smart, Tim (2006). A Dictionary of Modern Star names: A Short Guide to 254 Star Names and Their Derivations. Cambridge, Massachusetts: Sky Publishing Corp.. p. 50. ISBN 978-1-931559-44-7. 
  25. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日
  26. ↑ Neuhäuser, R; Torres, G; Mugrauer, M; Neuhäuser, D L; Chapman, J; Luge, D; Cosci, M (2022-07-29). "Colour evolution of Betelgeuse and Antares over two millennia, derived from historical records, as a new constraint on mass and age". Monthly Notices of the Royal Astronomical Society 516 (1): 693–719. doi:10.1093/mnras/stac1969. ISSN 0035-8711. 
  27. ↑ Kelley, David H.; Milone, Eugene F. (2011). Exploring Ancient Skies: A Survey of Ancient and Cultural Astronomy. Aveni, Berlin: Springer. p. 345. https://books.google.com/books?id=ILBuYcGASxcC. 
  28. ↑ 28.0 28.1 Lee, Byeong-Cheol et al. (October 2023). "Long-period radial velocity variations of nine M red giants: The detection of sub-stellar companions around HD 6860 and HD 112300". Astronomy & Astrophysics 678: A106. doi:10.1051/0004-6361/202243725. Bibcode: 2023A&A...678A.106L. 

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Further reading

  • 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

Coordinates: Sky map 01h 09m 43.9236s, +35° 37′ 14.008″



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