Gamma Andromedae

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Andromeda constellation, with γ And at top left of the main figure

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[1]) 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.[2] 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.[2][3]

Nomenclature[edit]

Stellar properties[edit]

Components of the γ Andromedae system (not to scale)
γ1 Andromedae
(γ Andromedae A)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 02h 03m 53.9531s[13]
Declination +42° 19′ 47.009″[13]
Apparent magnitude (V) 2.10[13]
Characteristics
Spectral type K3IIb[14]
U−B color index +1.58[14]
B−V color index +1.37[14]
R−I color index +0.68[14]
Astrometry
Radial velocity (Rv)−11.7 ± 0.9[13] km/s
Proper motion (μ) RA: 43.08[13] mas/yr
Dec.: −50.85[13] mas/yr
Parallax (π)9.19 ± 0.73[13] mas
Distance350 ± 30 ly
(109 ± 9 pc)
Absolute magnitude (MV)−2.9[15]
Details
Radius80[16] R
Luminosity2,000[16] L
Temperature4,500[16] K
Rotational velocity (v sin i)< 17[14] 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.[13][14][17]
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.[14]

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)

   (spectroscopic binary)[20]
A0V (C)[21]

U−B color index −0.12[19]
B−V color index +0.03[19]
Astrometry
Radial velocity (Rv)−14 ± 5 (B)[22] km/s
Proper motion (μ) RA: 37 (B)[22] mas/yr
Dec.: −57 (B)[22] mas/yr
Parallax (π)9.19 ± 0.73[18] mas
Distance350 ± 30 ly
(109 ± 9 pc)
Absolute magnitude (MV)−0.3 (BC)[15]
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 [17]
Position angle63° [17]
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.[22][17]
Database references
SIMBADdata

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.[17]

In October 1842, Wilhelm Struve found that γ2 Andromedae was itself a double star whose components were separated by less than an arcsecond.[6] 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.[20]

Location[edit]

The star's location is shown in the following chart of the Andromeda constellation:

Almach as a name[edit]

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

See also[edit]

References[edit]

  1. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017. 
  2. ^ 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.
  3. ^ 01578+4151, database entry, MSC - a catalogue of physical multiple stars, A. A. Tokovinin, CDS database ID J/A+AS/124/75.
  4. ^ 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:1012.0707Freely accessible [astro-ph.SR]. 
  5. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  6. ^ a b c p. 36–37, Star-names and Their Meanings, Richard Hinckley Allen, New York: G. E. Stechert, 1899.
  7. ^ p. 23, Star tales, Ian Ridpath, James Clarke & Co., 1989, ISBN 0-7188-2695-7.
  8. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日
  9. ^ 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. 
  10. ^ 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.
  11. ^ 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, Bibcode1998JBAA..108....9R.
  12. ^ p.27, Star Lore of All Ages, William Tyler Olcott, G.P. Putnam's Sons, New York and London, The Knickerbocker Press, 1911
  13. ^ a b c d e f g h "* gam01 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 19, 2008. 
  14. ^ 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.
  15. ^ a b From apparent magnitude and parallax.
  16. ^ a b c Almach, Jim Kaler, Stars. Accessed on line August 19, 2008.
  17. ^ 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.
  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. ^ a b 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, Bibcode1960ApJ...131..119M.
  21. ^ 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.
  22. ^ a b c d "* gam02 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 19, 2008. 
  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.

External links[edit]

Coordinates: Sky map 02h 03m 53.9531s, +42° 19′ 47.009″