Gamma Andromedae

From Wikipedia, the free encyclopedia
(Redirected from Almach)
Jump to navigation Jump to search

Template:Short description Template:Hatnote group

Template:Starbox visbin

γ1 Andromedae
(γ Andromedae A)
Template:Location mark
Location of γ Andromedae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 2.27[2]
Characteristics
Evolutionary stage Candidate post-AGB[3]
Spectral type K2+IIb[4]
U−B Template:Engvar +1.58[2]
B−V Template:Engvar +1.37[2]
R−I Template:Engvar +0.68[2]
Astrometry
Radial velocity (Rv)Template:Val[5] km/s
Proper motion (μ) RA: +42.32[1] mas/yr
Dec.: −49.30[1] mas/yr
Parallax (π)8.30±1.04 mas[1]
Distanceapprox. Template:Rnd ly
(approx. Template:Rnd pc)
Absolute magnitude (MV)−3.09
Details
Radius98.5[6] Template:Solar radius
LuminosityTemplate:Val[6] Template:Solar luminosity
Surface gravity (log g)1.03[7] cgs
Temperature4,248[7] K
Metallicity [Fe/H]−0.06[3] dex
Rotational velocity (v sin i)< 17[2] km/s
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[2][8][9]
Database references
SIMBADdata

Script error: No such module "Check for unknown parameters".

Gamma Andromedae is a multiple star system in the northern constellation of Andromeda. It is the third-brightest star in the constellation, after Alpheratz and Mirach. Its identifier is a Bayer designation that is Latinized from γ Andromedae, and is abbreviated Gam1 And or γ1 And, respectively. The system has the proper name Almach, pronounced Template:IPAc-en. Based on parallax measurements, it is estimated to be about 390 light-years distant. The system is drifting closer to the Sun with a radial velocity of Template:Val.[5]

Observation

File:Almach double star.jpg
An image of γ Andromedae as it appears in a small telescope

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.[10]

The brighter member, γ1 Andromedae, is the primary of the system, and is thus designated component γ Andromedae A. It has the official proper name Almach Template:IPAc-en, which was used as the traditional name of the naked eye star, and thus the system as a whole.[11][12] The fainter secondary is γ2 Andromedae or γ Andromedae B. 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.[10][13]

File:Almach dpeach crop.jpg
Almach star system showing A, B and C components

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).[14] In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] 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.[12]

Almach was the traditional name (also spelt as Almaach, Almaack, Almak, Almaak, or Alamak), derived from the Arabic العناق (al-‘anāq),[16] "the caracal" (desert lynx).[17] Another term for this star used by medieval astronomers writing in Arabic was رجل المسلسلة (Rijl al Musalsalah), "Foot of The [Chained] Woman".[16] 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.[18][19]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), 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 Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[20]

In the Babylonian star catalogues, γ Andromedae, together with Triangulum, formed the constellation known as MULAPIN (Template:Script) "The Plough".[21] Astrologically, this star was considered "honourable and eminent".[22]

Stellar properties

File:Gamma Andromedae Components Black.svg
Gamma Andromedae Components

Template:Starbox visbin Template:Starbox relpos

γ2 Andromedae
(γ Andromedae BC)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension Template:RA (B)[23]
Declination Template:DEC (B)[23]
Apparent magnitude (V) 4.84 (BC combined)

5.5 (B)
6.3 (C)[24]

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

A0V (C)[25]

U−B Template:Engvar −0.12[24]
B−V Template:Engvar +0.03[24]
Astrometry
B
Radial velocity (Rv)Template:Val[5] km/s
Proper motion (μ) RA: 30.021[26] mas/yr
Dec.: −51.640[26] mas/yr
Parallax (π)9.19±0.73 mas[27]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Details[27]
Ba
MassTemplate:Val Template:Solar mass
Bb
MassTemplate:Val Template:Solar mass
Metallicity [Fe/H]{{{metal_fe2}}} dex
C
MassTemplate:Val Template:Solar mass
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[28][9]
Database references
SIMBADdata

Script error: No such module "Check for unknown parameters".

γ1 Andromedae A is a massive bright giant star with a spectral classification of K2+IIb.[4] The star has an apparent visual magnitude of approximately 2.26.[2] It has been classified as a candidate post-asymptotic giant branch (AGB) star.[3] However, it does not display a chemical enhancement of s-process elements typical of an AGB star.[29]

The γ2 Andromedae BC sub-system, with an overall apparent visual magnitude of 4.84,[24] is 9.6 arcseconds away from γ1 Andromedae at a position angle of 63 degrees.[9]

γ1 and γ2 have an orbital period of approximately 5,000 years.[30]

In October 1842, Wilhelm Struve found that γ2 Andromedae was itself a double star whose components were separated by less than an arcsecond.[16] 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.[24] They have an orbital period of about 64 years and a high eccentricity of 0.927.[27] 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.[31] The two orbits may be coplanar.[27] As of 2019, the angular distance between the B and C stars was 0.16 arcsecond.[32]

Almach as a name

Template:USS was the name of a United States navy ship.

See also

References

Template:Reflist

External links

Template:Sky Template:Stars of Andromeda

  1. ↑ a b c d e Script error: No such module "Citation/CS1".
  2. ↑ a b c d e f g Script error: No such module "citation/CS1". Script error: No such module "citation/CS1".
  3. ↑ a b c Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "Citation/CS1".
  5. ↑ a b c Script error: No such module "Citation/CS1".
  6. ↑ a b Script error: No such module "Citation/CS1". Gamma Andromedae's database entry at VizieR.
  7. ↑ a b Script error: No such module "Citation/CS1".
  8. ↑ Template:Cite simbad
  9. ↑ a b c Script error: No such module "Citation/CS1". Script error: No such module "citation/CS1".
  10. ↑ a b Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ a b Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ a b c Script error: No such module "citation/CS1".
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日 Template:Webarchive
  21. ↑ Script error: No such module "Citation/CS1".
  22. ↑ Script error: No such module "citation/CS1".
  23. ↑ a b Component 2, HIP 9640, database entry, Hipparcos catalogue, CDS ID I/239.
  24. ↑ a b c d e Script error: No such module "citation/CS1". Script error: No such module "citation/CS1".
  25. ↑ Entry 02039+4220, discoverer code STT  38BC, The Washington Double Star Catalog Template:Webarchive, United States Naval Observatory. Accessed on line August 19, 2008.
  26. ↑ a b Template:Cite DR2
  27. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named orb2
  28. ↑ Template:Cite simbad
  29. ↑ Script error: No such module "Citation/CS1".
  30. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named orb1
  31. ↑ Script error: No such module "Citation/CS1".
  32. ↑ Script error: No such module "citation/CS1".
Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Gamma_Andromedae&oldid=1095951"