Epoch J2000 Equinox J2000
|Right ascension||21h 53m 55.72620s|
|Declination||–37° 21′ 53.4790″|
|Apparent magnitude (V)||3.003|
|Spectral type||B8 III|
|U−B color index||–0.307|
|B−V color index||–0.121|
|Radial velocity (Rv)||–2.1 km/s|
|Proper motion (μ)||RA: +98.07 mas/yr
Dec.: –13.22 mas/yr
|Parallax (π)||15.45 ± 0.67 mas|
|Distance||211 ± 9 ly
(65 ± 3 pc)
|Rotational velocity (v sin i)||57 km/s|
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)" and once belonged to the Ptolemaic constellation Piscis Austrinus. With an apparent visual magnitude of 3.0, 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. Consequently, γ Gruis itself is known as 敗臼一 (Bài Jiù yī, English: the First Star of Decayed Mortar.)
Based upon parallax measurements, this star is located at a distance of roughly 211 light-years (65 parsecs) from Earth. Analysis of the spectrum shows it to match a stellar classification of B8 III, 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. Its outer envelope has an effective temperature of 12,520 K, which give the star a blue-white hue. Gamma Gruis is rotating relatively rapidly with a projected rotational velocity of 57 km s–1. By way of comparison, the Sun has an azimuthal velocity along its equator of just 2 km s–1.
See also 
- 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
- Gutierrez-Moreno, Adelina et al. (1966). A System of photometric standards 1. Publicaciones Universidad de Chile, Department de Astronomy. pp. 1–17. Bibcode:1966PDAUC...1....1G.
- Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H
- Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institute of Washington D.C. Bibcode:1953GCRV..C......0W.
- 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
- 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, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147
- 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/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943
- "HD 207971 -- Star", SIMBAD Astronomical Database (Centre de Données astronomiques de Strasbourg), retrieved 2007-03-30
- 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
- (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.
- (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 5 日
- Kaler, James B., "AL DHANAB (Gamma Gruis)", Stars (University of Illinois), retrieved 2012-02-11
- 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/0612449, Bibcode:2007A&A...464..377F, doi:10.1051/0004-6361:20065526