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γ Andromedae
(γ Andromedae A)

Location of γ Andromedae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Andromeda
Right ascension	02 03 53.95229
Declination	+42° 19′ 47.0223″
Apparent magnitude (V)	2.27
Characteristics
Evolutionary stage	Candidate post-AGB
Spectral type	K2+IIb
U−B color index	+1.58
B−V color index	+1.37
R−I color index	+0.68
Astrometry
Radial velocity (Rv)	−11.7±0.9 km/s
Proper motion (μ)	RA: 42.32 mas/yr Dec.: −49.30 mas/yr
Parallax (π)	8.30 ± 1.04 mas
Distance	approx. 390 ly (approx. 120 pc)
Absolute magnitude (MV)	-3.09
Details
Radius	98.5 R☉
Luminosity	2987±412 L☉
Surface gravity (log g)	1.03 cgs
Temperature	4,248 K
Metallicity	−0.06 dex
Rotational velocity (v sin i)	< 17 km/s
Orbit
Primary	γ Andromedae
Companion	γ Andromedae
Period (P)	4,748 yr
Other designations
Almach, Almaach, Almak, Almaak, Alamak, γ And, Gamma Andromedae, Gamma And, γ Andromedae A, γ And A, Gamma Andromedae A, Gamma And A, 57 Andromedae A, 57 And A, BD+41 395, FK5 73, GC 2477, HD 12533, HIP 9640, HR 603, SAO 37734, PPM 44721, ADS 1630 A, CCDM J02039+4220A, WDS 02039+4220A
Database references
SIMBAD	data

Gamma Andromedae, Latinized from γ Andromedae, is the third-brightest point of light in the northern constellation of Andromeda. It is a multiple star system approximately 390 light-years from Earth. The system is drifting closer to the Sun with a radial velocity in the range of −12 to −14 km/s.

Observation

In 1778, German physicist Johann Tobias Mayer discovered that γ Andromedae is a double star. When examined in a small telescope, it appears to be a bright, golden-yellow star next to a dimmer, indigo-blue star, separated by approximately 10 arcseconds. The pair is often considered by stargazers to be a beautiful double star with a striking contrast of color.

The brighter member, γ Andromedae, is the primary of the system, and is thus designated component γ Andromedae A. It has the official proper name Almach /ˈælmæk/, which was used as the traditional name of the naked eye star, and thus the system as a whole. The fainter secondary is γ Andromedae or γ Andromedae B. It was later discovered that γ Andromedae is itself a triple star system. What appears as a single star to the naked eye is thus a quadruple star system.

Nomenclature

γ Andromedae (Latinised to Gamma Andromedae) is the system's Bayer designation; γ and γ Andromedae those of its two constituents. The designations of those constituents as Gamma Andromedae A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Almach for the component Gamma Andromedae A on 20 July 2016 and it is now so included in the List of IAU-approved Star Names.

Almach was the traditional name (also spelt as Almaach, Almaack, Almak, Almaak, or Alamak), derived from the Arabic العناق (al-‘anāq), "the caracal" (desert lynx). Another term for this star used by medieval astronomers writing in Arabic was رجل المسلسلة (Rijl al Musalsalah), "Foot of The Woman". In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated الخامس النعامة (Al Khamis al Na'amah), which was translated into Latin as Quinta Struthionum, meaning the fifth ostrich.

In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of γ Andromedae, φ Persei, 51 Andromedae, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, β Trianguli, γ Trianguli and δ Trianguli. Consequently, the Chinese name for γ Andromedae itself is 天大將軍一 (Tiān Dà Jiāng Jūn yī, English: the First Star of Heaven's Great General).

In the Babylonian star catalogues, γ Andromedae, together with Triangulum, formed the constellation known as APIN (𒀯𒀳) "The Plough". Astrologically, this star was considered "honourable and eminent".

Stellar properties

γ Andromedae A is a massive bright giant star with a spectral classification of K2+IIb. The star has an apparent visual magnitude of approximately 2.26. The star has been classified as a candidate post-asymptotic giant branch star. However, it does not display a chemical enhancement of s-process elements typical of an AGB star.

γ Andromedae BC, with an overall apparent visual magnitude of 4.84, is 9.6 arcseconds away from γ Andromedae at a position angle of 63 degrees.

γ and γ have an orbital period of approximately 5,000 years.

In October 1842, Wilhelm Struve found that γ Andromedae was itself a double star whose components were separated by less than an arcsecond. The components are an object of apparent visual magnitude 5.5, γ Andromedae B, and an A-type main-sequence star with apparent visual magnitude 6.3, γ Andromedae C. They have an orbital period of about 64 years and a high eccentricity of 0.927. Spectrograms taken from 1957 to 1959 revealed that γ Andromedae B was itself a spectroscopic binary, composed of two B-type main-sequence stars orbiting each other with a period of 2.67 days. The two orbits may be coplanar. As of 2019, the angular distance between the B and C stars was 0.16 arcsecond.

Almach as a name

USS Almaack (AKA-10) was the name of United States navy ship.

See also

• NGC 752

References

1. ^ van Leeuwen, F. (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, S2CID 18759600.
2. ^ Hoffleit, Dorrit; Jaschek, Carlos (1991). The Bright star catalogue. Bibcode:1991bsc..book.....H. "database entry". CDS. Retrieved 2019-11-19.
3. ^ Rao, S. Sumangala; Giridhar, Sunetra; Lambert, David L. (January 2012). "Chemical composition of a sample of candidate post-asymptotic giant branch stars". Monthly Notices of the Royal Astronomical Society. 419 (2): 1254–1270. Bibcode:2012MNRAS.419.1254R. doi:10.1111/j.1365-2966.2011.19780.x.
4. ^ Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373, S2CID 123149047.
5. ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
6. ^ 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, arXiv:1706.02208, doi:10.1093/mnras/stx1433, ISSN 0035-8711 Gamma Andromedae's database entry at VizieR.
7. ^ Luck, R. Earle (2014-06-01). "Parameters and Abundances in Luminous Stars". The Astronomical Journal. 147 (6): 137. Bibcode:2014AJ....147..137L. doi:10.1088/0004-6256/147/6/137. ISSN 0004-6256.
8. ^ Tokovinin, A. A. "HIP 9640". Multiple Star Catalogue. Archived from the original on 2020-10-02. Retrieved 2019-11-19.
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11. ^ Robert Burnham (1 January 1978). Andromeda-Cetus. Courier Corporation. ISBN 978-0-486-23567-7.
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13. ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.
14. A. A. Tokovinin. "MSC - a catalogue of physical multiple stars". CDS. Retrieved 2019-11-19.
15. Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 .
16. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
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18. Ridpath, Ian (1988). Star Tales. James Clarke & Co. ISBN 0-7188-2695-7.
19. Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
20. Richard H. Allen (28 February 2013). Star Names: Their Lore and Meaning. Courier Corporation. ISBN 978-0-486-13766-7. η Cet (Deneb Algenubi), θ Cet (Deneb Algenubi), τ Cet (Durre Menthor), ζ Cet (Baten Kaitos), and υ Cet, were Al Naʽāmāt, the Hen Ostriches.
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22. Rogers, J. H. (1998). "Origins of the ancient constellations: I. The Mesopotamian traditions". Journal of the British Astronomical Association. 108: 9. Bibcode:1998JBAA..108....9R.
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25. ^ Hoffleit, Dorrit; Jaschek, Carlos (1991). The Bright star catalogue. Bibcode:1991bsc..book.....H. "database entry". CDS. Retrieved 2019-11-19.
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External links

• Almaak (Gamma Andromedae) at The Internet Encyclopedia of Science
• Image ALMACH
• Almaak on AstroDwarf
• Gamma Andromedae on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

v t e Constellation of Andromeda
Adhil Andromeda in Chinese astronomy List of Andromeda's satellite galaxies List of stars in Andromeda
Stars	Bayer α (Alpheratz) β (Mirach) γ (Almach) δ ε ζ η θ ι κ λ μ ν ξ (Adhil) ο π ρ σ τ υ (Titawin) φ χ ψ ω A b c υ Per (Nembus) Flamsteed 2 3 4 5 6 7 8 9 10 11 12 13 14 (Veritate) 15 18 22 23 26 28 32 36 39 41 44 45 47 55 56 58 59 63 64 65 66 6 Per Variable R T U W Z RT RV RX SU SW TU TW WZ XZ AB AC AD AE AF AR BM BX CC CG CN DS DX EG ET EU FF GO GP GQ GX GR GY HH HN IW KK KX KZ LL LN LP LQ OP OS OU PX PY QR QV QX V385 V428 V439 V455 V529 V807 HR 1 40 56 78 104 122 134 178 275 282 283 289 379 410 483 687 746 748 8884 8925 8950 8962 8973 9011 9074 9075 9105 HD 16175 (Buna) 222155 Other 3XMM J004232.1+411314 ADS 48 HAT-P-6 (Sterrennacht) HAT-P-16 HAT-P-19 HAT-P-28 M31-RV KELT-1 NGC 44 NGC 82 NGC 84 NGC 91 NGC 162 NGC 464 Qatar-3 Qatar-4 Qatar-5 PA-99-N2 WASP-1 WISE 0146+4234 WISE J0005+3737 WISE J004945.61+215120.0
Exoplanets 14 Andromedae b κ Andromedae b υ Andromedae b c d Gliese 15 Ab c HD 13931 b HD 16175 b HAT-P-6b HAT-P-32b WASP-1b WASP-33b Qatar-4b Qatar-5b
Star clusters	NGC 206 272 752 956 7686 Other Mayall II RBC EXT8
Nebulae	NGC 7662
Galaxies	Messier 32 110 NGC 5 11 13 19 20 21 27 39 43 48 49 51 67 68 69 70 71 72 74 76 79 80 81 83 85 86 90 93 94 96 97 108 109 112 140 149 160 169 181 183 184 214 218 226 228 229 233 243 252 258 260 262 280 304 317 389 393 404 425 431 477 512 513 523 528 529 531 536 542 561 605 620 668 679 687 700 703 704 705 708 709 710 712 714 717 721 732 753 759 801 812 834 891 906 910 911 912 913 920 937 980 995 996 999 1000 7640 7836 Numbered I II III IV V VIII IX X XI XVIII XIX XXI Other 3C 66A 3C 66B Andromeda Galaxy Arp 273 Donatiello I UGC 1840
Galaxy clusters Abell 262 NGC 68 group
Astronomical events GRB 101225A SN 1885A (S)
Category

• Multiple star systems
• Multiple stars
• Spectroscopic binaries
• K-type bright giants
• B-type main-sequence stars
• A-type main-sequence stars
• Andromeda (constellation)
• Bayer objects
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Bright Star Catalogue objects
• Hipparcos objects
• Stars with proper names