Gamma Arietis

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Gamma Arietis
Diagram showing star positions and boundaries of the Aries constellation and its surroundings
Cercle rouge 100%.svg

Location of γ Arietis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aries
Right ascension 01h 53m 31.81479s[1]
Declination +19° 17′ 37.8790″[1]
Apparent magnitude (V) 3.86 (4.58/4.64)[2]
Spectral type B9 V + A1p Si[2]
U−B color index –0.12[3]
B−V color index –0.04[3]
Radial velocity (Rv) +3.7[4] km/s
Proper motion (μ) RA: +79.20[1] mas/yr
Dec.: –97.63[1] mas/yr
Parallax (π) 19.88 ± 0.96[1] mas
Distance 164 ± 8 ly
(50 ± 2 pc)
Gam1 Ari
Radius 1.9[5] R
Rotational velocity (v sin i) 54[6] km/s
Gam2 Ari
Surface gravity (log g) 4.25[7] cgs
Temperature 10,970[7] K
Metallicity [Fe/H] 0.43 ± 0.14[8] dex
Rotational velocity (v sin i) 201[6] km/s
Other designations
5 Ari, BD+18 243, HIP 8832.[9]
Gam1 Ari: HD 11502, HR 545, SAO 92680.
Gam2 Ari: HD 11503, HR 546, SAO 92681.

Gamma Arietis (γ Ari, γ Arietis) is the Bayer designation for a binary star system in the northern constellation of Aries. It has the traditional name Mesarthim, which is of obscure origin.[10] The combined apparent visual magnitude of the two stars is 3.86,[2] which is readily visible to the naked eye and makes this the fourth brightest member of Aries. Based upon an annual parallax shift of 19.88 mas,[1] the distance to Gamma Arietis is approximately 164 light-years (50 parsecs).

The double star nature of this system was discovered by Robert Hooke in 1664.[11] The two components have an angular separation of 7.606 arcseconds,[2] which can be resolved with a small telescope. The orbital period of the pair is greater than 5000 years.[12] The brighter component, γ¹ Arietis, is a magnitude 4.58 B-type main sequence star with a stellar classification of B9 V.[2] The secondary, γ² Arietis, is a Lambda Boötis[7] (chemically peculiar) star with a stellar classification of A1p Si and a magnitude of 4.64.[2] It is classified as an α2 CVn type variable star and its brightness varies by 0.04 magnitudes with a period of 2.61 days.

In culture[edit]

It has the traditional name Mesarthim, of obscure origin, and has been called "the First Star in Aries" as having been at one time the nearest visible star to the equinoctial point. The name Mesarthim may be from the Hebrew word mᵋshārᵋtīm, meaning "the minister",[10] or the Arabic word Al Muthartim (ألمثرتم), meaning "the ram".[13] The meaning "servants" has also been suggested.[14] In Sanskrit, the Aeris is known as Mesha (The ram) and the First point of Aries is Meshadi. The name could have very well originated from this and transformed to Mesarthim.

In Chinese, 婁宿 (Lóusù), meaning Bond (asterism), refers to an asterism consisting of γ Arietis, β Arietis and α Arietis.[15] Consequently, α Arietis itself is known as 婁宿二 (Lóusù Èr, English: the Second Star of Bond.)[16]

In Hindu astrology, Beta Arietis (Sheratan) and Gamma Arieties (Mesartim) are Ashwinis, the twin gods who act as doctors of the divine of the world.(Richard H Allen)


  1. ^ a b c d e f van Leeuwen, F. (November 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. 
  2. ^ a b c d e f Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  3. ^ a b Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series 34: 1–49, Bibcode:1978A&AS...34....1N. 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W. 
  5. ^ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  6. ^ a b Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943. 
  7. ^ a b c Gerbaldi, M.; Faraggiana, R.; Lai, O. (December 2003), "The heterogeneous class of lambda Bootis stars", Astronomy and Astrophysics 412: 447–464, Bibcode:2003A&A...412..447G, doi:10.1051/0004-6361:20031472. 
  8. ^ Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics 525: A71, arXiv:1009.1491, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014. 
  9. ^ "gam Ari -- Variable Star of alpha2 CVn type", SIMBAD Astronomical Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-08-04. 
  10. ^ a b Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 82, ISBN 0-486-21079-0, retrieved 2010-12-12 
  11. ^ Aitken, Robert G. (1935), The Binary Stars, New York: McGraw-Hill, p. 1 
  12. ^ Kaler, James B., "Mesarthim", Stars (University of Illinois), retrieved 2012-08-04. 
  13. ^ Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy LII (3): 13, Bibcode:1944PA.....52....8D 
  14. ^ "Star names from the National Astronomy and Ionosphere Center". Retrieved 18 October 2012. 
  15. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  16. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.

External links[edit]