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Gamma Andromedae

Coordinates: Sky map 02h 03m 53.9531s, +42° 19′ 47.009″
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Not to be confused with Y Andromedae.
γ1 Andromedae
(γ Andromedae A)
Location of γ Andromedae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 02h 03m 53.9531s[1]
Declination +42° 19′ 47.009″[1]
Apparent magnitude (V) 2.10[1]
Characteristics
Spectral type K3IIb[2]
U−B color index +1.58[2]
B−V color index +1.37[2]
R−I color index +0.68[2]
Astrometry
Radial velocity (Rv)−11.7 ± 0.9[1] km/s
Proper motion (μ) RA: 43.08[1] mas/yr
Dec.: −50.85[1] mas/yr
Parallax (π)9.19 ± 0.73 mas[1]
Distance350 ± 30 ly
(109 ± 9 pc)
Absolute magnitude (MV)−3.05[3]
Details
Radius80[4] R☉
Luminosity2,000[4] L☉
Temperature4,500[4] K
Rotational velocity (v sin i)< 17[2] km/s
Other designations
Almach, Almaach, Almak, Almaak, Alamak, γ1 And, Gamma1 Andromedae, Gamma1 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.[1][2][5]
Database references
SIMBADdata

Gamma Andromedae (γ Andromedae, abbreviated Gam 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.

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, also named Almach[6]) 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.[7] 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.[7][8]

Nomenclature

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 02h 03m 54.720s (B)[18]
Declination +42° 19′ 51.41″ (B)[18]
Apparent magnitude (V) 4.84 (BC combined)

5.5 (B)
6.3 (C)[19]

Characteristics
Spectral type B9.5V/B9.5V (B)

A0V (C)[20]

U−B color index −0.12[19]
B−V color index +0.03[19]
Astrometry
B
Radial velocity (Rv)−14±5[21] km/s
Proper motion (μ) RA: 37[21] mas/yr
Dec.: −57[21] mas/yr
Parallax (π)9.19 ± 0.73 mas[18]
Distance350 ± 30 ly
(109 ± 9 pc)
Absolute magnitude (MV)−0.3 (BC combined)[22]
Orbit[23]
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 γ1 And)
Epoch of observation2004
Angular distance9.6″ [5]
Position angle63° [5]
Other designations
γ2 And, Gamma2 Andromedae, Gamma2 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.[21][5]
Database references
SIMBADdata

γ1 Andromedae is a bright giant star with a spectral classification of K3IIb. It has an apparent visual magnitude of approximately 2.26.[2]

γ2 Andromedae, with an overall apparent visual magnitude of 4.84,[19] is 9.6 arcseconds away from γ1 Andromedae at a position angle of 63 degrees.[5]

In October 1842, Wilhelm Struve found that γ2 Andromedae was itself a double star whose components were separated by less than an arcsecond.[11] 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.[19] They have an orbital period of about 64 years.[23] 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.[24]

Almach as a name

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

See also

References

  1. ^ a b c d e f g h "* gam01 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 19, 2008.
  2. ^ a b c d e f g HR 603, 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 19, 2008.
  3. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. {{citation}}: Unknown parameter |class= ignored (help)
  4. ^ a b c Almach, Jim Kaler, Stars. Accessed on line August 19, 2008.
  5. ^ a b c d e Entry 02039+4220, discoverer code STF 205, components A-BC, The Washington Double Star Catalog Archived 2006-02-20 at the Wayback Machine, United States Naval Observatory. Accessed on line August 27, 2008.
  6. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  7. ^ a b pp. 113–114, vol. 1, Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Robert Burnham, New York: Courier Dover Publications, 1978, ISBN 0-486-23567-X.
  8. ^ 01578+4151, database entry, MSC - a catalogue of physical multiple stars, A. A. Tokovinin, CDS database ID J/A+AS/124/75.
  9. ^ 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].
  10. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  11. ^ a b c p. 36–37, Star-names and Their Meanings, Richard Hinckley Allen, New York: G. E. Stechert, 1899.
  12. ^ p. 23, Star tales, Ian Ridpath, James Clarke & Co., 1989, ISBN 0-7188-2695-7.
  13. ^ Template:Zh icon AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日
  14. ^ 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: 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  15. ^ 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 See Star Name - R.H.Allen p. 160. In Al Achsasi Al Mouakket catalogue, η Cet as Aoul al Naamat or Prima Struthionum (the first ostrich), θ Cet as Thanih al Naamat or Secunda Struthionum (the second ostrich), τ Cet as Thalath al Naamat or Tertia Struthionum (the third ostrich), and ζ Cet as Rabah al Naamat or Quarta Struthionum (the fourth ostrich). υ Cet should be Khamis al Naamat or Quinta Struthionum (the fifth ostrich) consistently, but Al Achsasi Al Mouakket designated the title the fifth ostrich to γ Gam with uncleared consideration.
  16. ^ Origins of the ancient constellations: I. The Mesopotamian traditions, J. H. Rogers, Journal of the British Astronomical Association 108, #1 (February 1998), pp. 9–28, Bibcode:1998JBAA..108....9R.
  17. ^ p.27, Star Lore of All Ages, William Tyler Olcott, G.P. Putnam's Sons, New York and London, The Knickerbocker Press, 1911
  18. ^ a b c Component 2, HIP 9640, database entry, Hipparcos catalogue, CDS ID I/239.
  19. ^ a b c d e HR 604, 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 19, 2008.
  20. ^ 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.
  21. ^ a b c d "* gam02 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 19, 2008.
  22. ^ From apparent magnitude and parallax.
  23. ^ a b Entry 02039+4220, Sixth Catalog of Orbits of Visual Binary Stars, William I. Hartkopf & Brian D. Mason, United States Naval Observatory. Accessed on line August 21, 2007.
  24. ^ A Preliminary Study of the Spectroscopic Binary Gamma Andromedae B, L. A. Maestre and J. A. Wright, Astrophysical Journal 131 (January 1960), pp. 119–121, Bibcode:1960ApJ...131..119M.


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