Epoch J2000 Equinox J2000
|Right ascension||14h 41m 55.75579s|
|Declination||–47° 23′ 17.5155″|
|Apparent magnitude (V)||2.30|
|Spectral type||B1.5 III|
|U−B color index||–0.88|
|B−V color index||–0.20|
|Variable type||Beta Cephei|
|Radial velocity (Rv)||+5.4 ± 0.6 km/s|
|Proper motion (μ)||RA: −20.94 mas/yr
Dec.: −23.67 mas/yr
|Parallax (π)||7.02 ± 0.17 mas|
|Distance||460 ± 10 ly
(142 ± 3 pc)
|Absolute magnitude (MV)||−4.3|
|Mass||10.1 ± 1.0 M☉|
|Surface gravity (log g)||3.46 cgs|
|Temperature||21,820 ± 2,160 K|
|Metallicity [Fe/H]||0.04 dex|
|Rotational velocity (v sin i)||16 km/s|
Alpha Lupi (α Lupi, α Lup) is the brightest star in the southern constellation of Lupus. According to the Bortle Dark-Sky Scale, the apparent visual magnitude of 2.3 makes it readily visible to the naked eye. Based upon parallax measurements made during the Hipparcos mission, the star is located at a distance of around 460 light-years (140 parsecs) from Earth.
Alpha Lupi is a giant star with a stellar classification of B1.5 III. It has about ten times the mass of the Sun but is radiating 25,000 times the Sun's luminosity. The outer atmosphere has an effective temperature of 21,820 K, which gives it the blue-white glow of a B-type star. In 1956 it was identified as a Beta Cephei variable, which means it undergoes periodic changes in luminosity because of pulsations in the atmosphere. The variability period is 0.29585 days, or just over 7 hours, 6 minutes. The magnitude varies by about 0.03, or about 3% of the total luminosity. A small star situated near Alpha Lupi may just be an optical companion.
This star is a proper motion member of the Upper-Centaurus Lupus sub-group in the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. This is a gravitationally unbound stellar association with an estimated age of 16–20 million years. The association is also the source of a bubble of hot gas that contains the Sun, known as the Local Bubble.
In Chinese, 騎官 (Qí Guān), meaning Imperial Guards, refers to an asterism consisting of α Lupi, γ Lupi, δ Lupi, κ Centauri, β Lupi, λ Lupi, ε Lupi, μ Lup, π Lupi and ο Lupi . Consequently, α Lupi itself is known as 騎官十 (Qí Guān shí, English: the Tenth Star of Imperial Guards.).
R. H. Allen had opinion that this star was listed it in the Chinese asterism Yang Mun or Men（南門), meaning "the South Gate", in his work Star-Names and their Meanings. But in Chinese astronomy, 南門 is located in Horn mansion and consisted by α and ε Centauri. Yang Mun was translated in Pinyin as 陽門, meaning "the Yang Gate", refers to the asterism in Neck mansion, containing the stars in Centaurus. Allen also suggested that the Babylonian name for the star was "Kakkab Su-gub Gud-Elim" (Star Left Hand of the Horned Bull).
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- (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) 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.]
- Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 279. ISBN 0-486-21079-0.
- Allen transliterated 南門 as Nan Mun in Centaurus.
Allen, R. H. (1963). Star Names: Their Lore and Meaning. p. 153.