Beta Andromedae

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Beta Andromedae
Andromeda IAU.svg
Red circle.svg
Location of β Andromedae (circled)
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 01h 09m 43.92388s [1]
Declination +35° 37′ 14.0075″ [1]
Apparent magnitude  (V)2.05 [2] (2.01 to 2.10) [3]
Characteristics
Evolutionary stage Asymptotic giant branch [4]
Spectral type M0 III [5]
U−B color index +1.96 [2]
B−V color index +1.57 [2]
V−R color index 0.9 [6]
R−I color index +1.00 [7]
Variable type Semiregular [3]
Astrometry
Radial velocity (Rv)0.06±0.13 [8]  km/s
Proper motion (μ)RA: 175.90 [1]   mas/yr
Dec.: −112.20 [1]   mas/yr
Parallax (π)16.52 ± 0.56  mas [1]
Distance 197 ± 7  ly
(61 ± 2  pc)
Absolute magnitude  (MV)−1.76 [9]
Details
Mass 2.49 [10]   M☉
Radius 100 [11]   R☉
Luminosity 1,995 [11]   L☉
Surface gravity (log g)1.52 [12]   cgs
Temperature 3,842 [12]   K
Metallicity [Fe/H]−0.05 [12]   dex
Rotational velocity (v sin i)7.2 [11]  km/s
Other designations
Mirach, Merach, Mirac, Mizar, β And, Beta Andromedae, Beta And, 43 Andromedae, 43 And, BD+34°198, FK5  42, GJ  53.3, 9044, HD  6860, HIP  5447, HR  337, SAO  54471, WDS 01097+3537A, LTT  10420, NLTT  3848 [6] [13]
Database references
SIMBAD data

Beta Andromedae, Latinized from β Andromedae, and officially named Mirach /ˈmaɪræk/ , [14] [15] is a prominent star in the northern constellation of Andromeda. It is 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. [16]

Contents

This star has an apparent visual magnitude of around 2.05, [2] varying between 2.01 and 2.10, [3] 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 Sun. [1] Its apparent magnitude is reduced by 0.06 by extinction due to gas and dust along the line of sight. [8] The star has a negligible radial velocity of 0.1 km/s, [8] but with a relatively large proper motion, traversing the celestial sphere at 0.208″ ·yr−1. [17]

Properties

A light curve for Beta Andromedae, plotted from Hipparcos data BetaAndLightCurve.png
A light curve for Beta Andromedae, plotted from Hipparcos data

Beta Andromedae is a single [19] red giant with a stellar classification of M0 III, [5] and is currently on the asymptotic giant branch of its evolution. [4] Since 1943 the spectrum of this star has been one of the stable anchor points by which other stars are classified. [20] It is suspected of being a semiregular variable star whose apparent visual magnitude varies from +2.01 to +2.10. [3] At this stage of the star's evolution, the outer envelope has expanded to around 100 times the size of the Sun. [11] It is radiating 1,995 [11] times the luminosity of the Sun at an effective temperature of 3,842  K . [12]

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), [21] 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 . [13] This word refers to Mirach's position at the left hip of the princess Andromeda. [22] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) [23] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 [24] 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). [25] Medieval astronomers writing in Arabic called β Andromedae 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. [13] [26] The star has also been called Cingulum and Ventrale. [13] This al-Ḥūt was an indigenous Arabic constellation, not the Western "Northern Fish" part of the constellation Pisces. [26] These names are not from the Arabic marāqq, loins, because it was never called al-Marāqq in Arabian astronomy. [26] 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. [13] [27]

In Chinese, 奎宿 (Kuí Sù), meaning Legs , 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, the Chinese name for β Andromedae itself is 奎宿九 (Kuí Sù jiǔ, English: the Ninth Star of Legs). [28]

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. [29]

Substellar companion

A 2023 study detected radial velocity variations in Beta Andromedae (HD 6860), showing evidence of a substellar companion, likely a brown dwarf. [30]

The Beta Andromedae planetary system [30]
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±0.01663.87+4.61
−4.31		0.28+0.10
−0.09		——

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References

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  13. 1 2 3 4 5 Allen, R. A. (1899), Star-names and Their Meanings, p. 36
  14. ↑ 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.
  15. ↑ "IAU Catalog of Star Names" . Retrieved 28 July 2016.
  16. ↑ Darling, David, "Mirach's Ghost (NGC 404)", The Internet Encyclopedia of Science, retrieved 2008-08-15
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  22. ↑ Mirach, MSN Encarta. Accessed on line August 19, 2008. Archived 2009-10-31.
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  24. ↑ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
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  26. 1 2 3 George A.Davis Jr. (1971) Selected List of Star Names, p. 5.
  27. ↑ 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.
  28. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日
  29. ↑ 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.
  30. 1 2 Lee, Byeong-Cheol; Do, Hee-Jin; et al. (July 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 . arXiv: 2307.15897 .

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