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Gamma Gruis

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
Declination –37° 21′ 53.4790″
Apparent magnitude (V) 3.003
Characteristics
Spectral type B8 III
U−B color index –0.307
B−V color index –0.121
Astrometry
Radial velocity (Rv) –2.1 km/s
Proper motion (μ) RA: +98.07 mas/yr
Dec.: –13.22 mas/yr
Parallax (π) 15.45 ± 0.67mas
Distance 211 ± 9 ly
(65 ± 3 pc)
Details
Radius 4.5 R
Temperature 12,520 K
Rotational velocity (v sin i) 57 km/s
Other designations
γ Gru, CPD−37° 9119, FK5 822, GC 30640, HD 207971, HIP 108085, HR 8353, SAO 213374.
Database references
SIMBAD data

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.


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Wikipedia

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