Gamma Andromedae

Gamma Andromedae (γ Andromedae, abbreviated Gamma And, γ And) is the third-brightest point of light in the constellation of Andromeda. It is a multiple star system approximately 350 light-years from the Earth.

γ¹ Andromedae
(γ Andromedae A)

Location of γ Andromedae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Andromeda
Right ascension	02^h 03^m 54.0^s[1]
Declination	+42° 19′ 47″[1]
Apparent magnitude (V)	2.27[1]
Characteristics
Spectral type	K3IIb[1]
U−B color index	+1.58[1]
B−V color index	+1.37[1]
R−I color index	+0.68[1]
Astrometry
Radial velocity (Rv)	−11.7 ± 0.9[2] km/s
Proper motion (μ)	RA: 43.08[3] mas/yr Dec.: −50.85[3] mas/yr
Parallax (π)	9.19 ± 0.73[3] mas
Distance	350 ± 30 ly (109 ± 9 pc)
Details
Radius	80[4] R☉
Luminosity	2,000[4] L☉
Temperature	4,500[4] K
Rotational velocity (v sin i)	< 17[1] km/s
Orbit[5]
Primary	γ^1 Andromedae
Companion	γ^2 Andromedae
Period (P)	4,748 yr
Other designations
Almach, Almaach, Almak, Almaak, Alamak, γ^1 And, Gamma^1 Andromedae, Gamma^1 And, γ Andromedae A, γ And A, Gamma Andromedae A, Gamma And A, 57 Andromedae A, 57 And A, STF 205A, ADS 1630 A, BD+41 395, CCDM J02039+4220A, FK5 73, GC 2477, HD 12533, HIP 9640, HR 603, IDS 01578+4151 A, PPM 44721, SAO 37734, WDS 02039+4220A[3][1][6]
Database references
SIMBAD	data

Observation

An image of γ Andromedae as it appears in a small telescope

In 1778, Johann Tobias Mayer discovered that γ Andromedae was a double star. When examined in a small telescope, it appears to be a bright, golden-yellow star (γ¹ Andromedae or γ Andromedae A, officially named Almach /ˈælmæk/, the traditional name for the entire system)[7][8] next to a dimmer, indigo-blue star (γ² Andromedae or γ Andromedae B), separated by approximately 10 arcseconds. It is often considered by stargazers to be a beautiful double star with a striking contrast of color.[9] It was later discovered that γ² Andromedae is itself a triple star system. What appears as a single star to the naked eye is thus a quadruple star system.[9][10]

Nomenclature

• γ Andromedae (Latinised to Gamma Andromedae) is the system's Bayer designation; γ¹ and γ² 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).[11]
• In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] 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.[8]
• Almach was the traditional name (also spelt as Almaach, Almaack, Almak, Almaak, or Alamak), derived from the Arabic العناق (al-‘anāq),[13] "the caracal" (desert lynx).[14]
• Another term for this star used by medieval astronomers writing in Arabic was رجل المسلسلة (Rijl al Musalsalah), "Foot of The [Chained] Woman".[13]
• 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).[15]
• 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.[16][17]
• In the Babylonian star catalogues, γ Andromedae, together with Triangulum, formed the constellation known as ^MULAPIN (𒀯𒀳) "The Plough".[18]
• Astrologically, this star was considered "honourable and eminent."[19]

Stellar properties

Components of the γ Andromedae system (not to scale)

γ² Andromedae
(γ Andromedae BC)

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Andromeda
Right ascension	02^h 03^m 54.720^s (B)[20]
Declination	+42° 19′ 51.41″ (B)[20]
Apparent magnitude (V)	4.84 (BC combined) 5.5 (B) 6.3 (C)[21]
Characteristics
Spectral type	B9.5V/B9.5V (B) A0V (C)[22]
U−B color index	−0.12[21]
B−V color index	+0.03[21]
Astrometry
B
Radial velocity (Rv)	−14.0±5[2] km/s
Proper motion (μ)	RA: 3730.021[23] mas/yr Dec.: −51.640[23] mas/yr
Parallax (π)	12.5653 ± 0.5881[23] mas
Distance	260 ± 10 ly (80 ± 4 pc)
Orbit[24]
Period (P)	63.67 ± 1.0 yr
Semi-major axis (a)	0.302 ± 0.001″
Eccentricity (e)	0.927 ± 0.03
Inclination (i)	109.8 ± 5.0°
Longitude of the node (Ω)	109.6 ± 5.0°
Periastron epoch (T)	B2015.5 ± 1.5
Argument of periastron (ω) (secondary)	183.4 ± 15.0°
Position (relative to γ^1 And)
Epoch of observation	2004
Angular distance	9.6″ [6]
Position angle	63° [6]
Other designations
γ^2 And, Gamma^2 Andromedae, Gamma^2 And, γ Andromedae BC, γ And BC, Gamma Andromedae BC, Gamma And BC, 57 Andromedae BC, 57 And BC, HD 12534, HIP 9640, HR 604, SAO 37735, WDS 02039+4220BC[25][6]
Database references
SIMBAD	data

γ¹ Andromedae (A component) is a bright giant star with a spectral classification of K3IIb. It has an apparent visual magnitude of approximately 2.26.[1]

γ² Andromedae (BC component), with an overall apparent visual magnitude of 4.84,[21] is 9.6 arcseconds away from γ¹ Andromedae at a position angle of 63 degrees.[6]

γ¹ and γ² have an orbital period of approximately 5,000 years.[5]

In October 1842, Wilhelm Struve found that γ² Andromedae was itself a double star whose components were separated by less than an arcsecond.[13] The components are an object of apparent visual magnitude 5.5, γ Andromedae B, and a type-A main sequence star with apparent visual magnitude 6.3, γ Andromedae C.[21] They have an orbital period of about 64 years.[24] Spectrograms taken from 1957 to 1959 revealed that γ Andromedae B was itself a spectroscopic binary, composed of two type-B main sequence stars orbiting each other with a period of 2.67 days.[26]

Almach as a name

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

See also

• Gamma Andromedae in fiction
• NGC 752

References

1. Hoffleit, Dorrit; Jaschek, Carlos (1991). The Bright star catalogue. Bibcode:1991bsc..book.....H. "database entry". CDS. Retrieved 2019-11-19.
2. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
3. "* gam01 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 19, 2008.
4. Jim Kaler. "Almach". Stars. Retrieved 2019-11-19.
5. Tokovinin, A. A. "HIP 9640". Multiple Star Catalogue. Retrieved 2019-11-19.
6. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. "02039+4220, components A-BC". The Washington Double Star Catalog. Archived from the original on 2006-02-20. Retrieved 2019-11-19.
7. 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.
8. "Naming Stars". IAU.org. Retrieved 16 December 2017.
9. Robert Burnham (1 January 1978). Andromeda-Cetus. Courier Corporation. ISBN 978-0-486-23567-7.
10. A. A. Tokovinin. "MSC - a catalogue of physical multiple stars". CDS. Retrieved 2019-11-19.
11. 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 [astro-ph.SR].
12. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
13. Richard Hinckley Allen (1899). Star-names and Their Meanings. New York: G.E. Stechert. pp. 36–37.
14. Ridpath, Ian (1988). Star Tales. ISBN 0-7188-2695-7.
15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日
16. 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.
17. 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.
18. 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.
19. William Tyler Olcott (December 1985). Star Lore of All Ages. Health Research Books. ISBN 978-0-7873-1096-7.
20. Component 2, HIP 9640, database entry, Hipparcos catalogue, CDS ID I/239.
21. Hoffleit, Dorrit; Jaschek, Carlos (1991). The Bright star catalogue. Bibcode:1991bsc..book.....H. "database entry". CDS. Retrieved 2019-11-19.
22. Entry 02039+4220, discoverer code STT  38BC, The Washington Double Star Catalog Archived 2006-02-20 at the Wayback Machine, United States Naval Observatory. Accessed on line August 19, 2008.
23. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
24. Entry 02039+4220, Sixth Catalog of Orbits of Visual Binary Stars Archived 2017-11-12 at the Wayback Machine, William I. Hartkopf & Brian D. Mason, United States Naval Observatory. Accessed on line August 21, 2007.
25. "* gam02 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 19, 2008.
26. Maestre, L. A.; Wright, J. A. (1960). "A Preliminary Study of the Spectroscopic Binary Gamma Andromedae B". The Astrophysical Journal. 131: 119. Bibcode:1960ApJ...131..119M. doi:10.1086/146813.

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