Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||01h 09m 43.92388s|
|Declination||+35° 37′ 14.0075″|
|Apparent magnitude (V)||2.05 (2.01 to 2.10)|
|Spectral type||M0 III|
|U−B color index||+1.96|
|B−V color index||+1.57|
|V−R color index||0.9|
|R−I color index||+1.00|
|Radial velocity (Rv)||0.06 ± 0.13 km/s|
|Proper motion (μ)||RA: 175.90 mas/yr
Dec.: −112.20 mas/yr
|Parallax (π)||16.52 ± 0.56 mas|
|Distance||197 ± 7 ly
(61 ± 2 pc)
|Absolute magnitude (MV)||–1.76|
|Surface gravity (log g)||1.52|
|Metallicity [Fe/H]||–0.05 dex|
|Rotational velocity (v sin i)||7.2 km/s|
Beta Andromedae (Beta And, β And, β Andromedae) is the Bayer designation for a prominent star in the northern constellation of Andromeda. It has the traditional name Mirach, which is also spelled Merach, Mirac, Mirak. β Andromedae is located northeast of the Great Square of Pegasus and is theoretically visible to all observers north of 54° S. The galaxy NGC 404, also known as Mirach's Ghost, is visible seven arc-minutes away.
This star has an average apparent visual magnitude of 2.05, which makes it the brightest star in the constellation. However, the luminosity varies slightly from magnitude +2.01 to +2.10. Based upon parallax measurements, it is located at a distance of roughly 197 light-years (60 parsecs) from Earth. The apparent magnitude of this star is reduced by 0.06 from extinction caused by the gas and dust along the line of sight.
Beta Andromedae is a red giant with a stellar classification of M0 III. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is suspected of being a semiregular variable star whose apparent visual magnitude varies from +2.01 to +2.10. At this stage of the star's evolution, the outer envelope has expanded to around 100 times the size of the Sun. It is radiating 1,995 times the luminosity of the Sun at an effective temperature of 3,842 K.
Naming and etymology 
- The name Mirach, and its variations, such as Mirac, Mirar, Mirath, Mirax, etc. (the name is spelled Merach in Burritt's The Geography of the Heavens) come from the star's description in the Alfonsine Tables of 1521 as super mizar. Here, mirat is a corruption of the Arabic ميزر mīzar "girdle", which appeared in a Latin translation of the Almagest. This word refers to Mirach's position at the left hip of the princess Andromeda.
- Medieval astronomers writing in Arabic called β Andromedae Janb al-Musalsalah (English: The Side of the Chained (Lady)); it was part of the 26th manzil (Arabian lunar mansion) Batn al-Hũt, the Belly of the Fish, or Qalb al-Hũt, the Heart of the Fish. The star has also been called Cingulum and Ventrale. This al-Hũt was an indigenous Arabic constellation, not the Western "Northern Fish" part of the constellation Pisces. These names are not from the Arabic marãqq, loins, because it was never called al-Marãqq in Arabian astronomy. Al Rishã', the Cord (of the well-bucket), on al-Sũfĩ's star map. It is origin of the proper name Alrescha for Alpha Piscium.
- In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of 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, β Andromedae itself is known as 奎宿九 (Kuí Sù jiǔ, English: the Ninth Star of Legs.)
- The people of Micronesia named this star as Kyyw "The Porpoise", and become once of Micronesian month name.
- Mirach is listed in MUL.APIN as KA.MUSH.I.KU.E, meaning "the Deleter" (the alternative star is α Cas).
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode:1966CoLPL...4...99J
- NSV 414, database entry, table of suspected variable stars, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al., CDS ID II/250.
- Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11 (1): 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333
- NAME MIRACH -- Variable Star, database entry, SIMBAD. Accessed on line August 12, 2008.
- HR 337, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line August 12, 2008.
- 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, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272
- Elgarøy, Øystein; Engvold, Oddbjørn; Lund, Niels (March 1999), "The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity", Astronomy and Astrophysics 343: 222–228, Bibcode:1999A&A...343..222E
- Mirach, Stars, Jim Kaler. Accessed on line August 13, 2008.
- Massarotti, Alessandro et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
- Soubiran, C. et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788
- Allen, R. A. (1899), Star-names and Their Meanings, p. 36
- Darling, David, "Mirach's Ghost (NGC 404)", The Internet Encyclopedia of Science, retrieved 2008-08-15
- 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, retrieved 2012-02-04
- p. 18, The Geography of the Heavens, Elijah Hinsdale Burritt, Hiram Mattison, and Henry Whitall, New York: Sheldon & Company, 1856.
- Mirach, MSN Encarta. Accessed on line August 19, 2008. Archived 2009-10-31.
- George A.Davis Jr. (1971) Selected List of Star Names, p. 5.
- ibid. p. 19.
- Kunitsch, P., Smart, T., (2006) A Dictionary of Modern Star names: A Shoert Guide to 254 Star Names and Their Derivations, Cambridge, Sky Publishing Corp., p. 50.
- (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日
- p. 345, Exploring Ancient Skies: A Survey of Ancient and Cultural Astronomy, David H. Kelley, Eugene F. Milone, Anthony F. (FRW) Aveni, Berlin, Springer, 2011.
- Rogers, J. H. (February 1998). "Origins of the ancient constellations: I. The Mesopotamian traditions". Journal of the British Astronomical Association, no.1 108: 9–28. Bibcode:1998JBAA..108....9R.
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
- Image MIRACH
- Beta Andromedae on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images