Gamma Gruis

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

Location of γ Gruis (circled) near the center
Observation data
Epoch J2000      Equinox J2000
Constellation Grus
Right ascension 21h 53m 55.72620s[1]
Declination –37° 21′ 53.4790″[1]
Apparent magnitude (V) 3.003[2]
Spectral type B8 III[3]
U−B color index –0.307[2]
B−V color index –0.121[2]
Radial velocity (Rv) –2.1[4] km/s
Proper motion (μ) RA: +98.07[1] mas/yr
Dec.: –13.22[1] mas/yr
Parallax (π) 15.45 ± 0.67[1] mas
Distance 211 ± 9 ly
(65 ± 3 pc)
Radius 4.5[5] R
Temperature 12,520[6] K
Rotational velocity (v sin i) 57[7] km/s
Other designations
γ Gru, CPD−37° 9119, FK5 822, GC 30640, HD 207971, HIP 108085, HR 8353, SAO 213374.[8]
Database references

Gamma Gruis (Gamma Gru, γ Gruis, γ Gru) is a star in the southern constellation of Grus. It is known as Al Dhanab, "the Tail (of the constellation of the Southern Fish)"[9] and once belonged to the Ptolemaic constellation Piscis Austrinus. With an apparent visual magnitude of 3.0,[2] it is the third-brightest star in the constellation.

In Chinese, 敗臼 (Bài Jiù), meaning Decayed Mortar, refers to an asterism consisting of γ Gruis, λ Gruis, γ Piscis Austrini and 19 Piscis Austrini.[10] Consequently, γ Gruis itself is known as 敗臼一 (Bài Jiù yī, English: the First Star of Decayed Mortar.)[11]

Based upon parallax measurements, this star is located at a distance of roughly 211 light-years (65 parsecs) from Earth.[1] Analysis of the spectrum shows it to match a stellar classification of B8 III,[3] with the luminosity class of III indicating this is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence. The luminosity of Gamma Gruis is around 390 times that of the Sun, with a significant portion of the energy emission being in the ultraviolet.[12] Its outer envelope has an effective temperature of 12,520 K,[6] which give the star a blue-white hue. Gamma Gruis is rotating relatively rapidly with a projected rotational velocity of 57 km s−1.[7] By way of comparison, the Sun has an azimuthal velocity along its equator of just 2 km s−1.

Based upon analysis of data collected during the Hipparcos mission, this star may have a proper motion companion that is causing gravitational perturbation of Gamma Gruis.[13]

See also[edit]


  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:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Gutierrez-Moreno, Adelina; et al. (1966). "A System of photometric standards". 1. Publicaciones Universidad de Chile, Department de Astronomy: 1–17. Bibcode:1966PDAUC...1....1G. 
  3. ^ a b Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, 
  4. ^ Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institute of Washington D.C. Bibcode:1953GCRV..C......0W. 
  5. ^ Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 
  6. ^ a b Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134Freely accessible, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147 
  7. ^ a b Royer, F.; et al. (2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i in the northern hemisphere", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255Freely accessible, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943 
  8. ^ "HD 207971 -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2007-03-30 
  9. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc., p. 238, ISBN 0-486-21079-0 
  10. ^ (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.
  11. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 5 日
  12. ^ Kaler, James B., "AL DHANAB (Gamma Gruis)", Stars, University of Illinois, retrieved 2012-02-11 
  13. ^ Frankowski, A.; Jancart, S.; Jorissen, A. (March 2007), "Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data", Astronomy and Astrophysics, 464 (1): 377–392, arXiv:astro-ph/0612449Freely accessible, Bibcode:2007A&A...464..377F, doi:10.1051/0004-6361:20065526