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Star in the constellation Lupus From Wikipedia, the free encyclopedia
Alpha Lupi (α Lupi, α Lup) is a blue giant star, and the brightest star in the southern constellation of Lupus. According to the Bortle Dark-Sky Scale, its apparent visual magnitude of 2.3[2] makes it readily visible to the naked eye even from highly light-polluted locales. Based upon parallax measurements made during the Hipparcos mission,[11] the star is around 460 light-years (140 parsecs) from the solar system.[1] It is one of the nearest supernova candidates.[12]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lupus |
| Right ascension | 14h 41m 55.75579s[1] |
| Declination | –47° 23′ 17.5155″[1] |
| Apparent magnitude (V) | 2.30[2] (2.29 - 2.34[3]) |
| Characteristics | |
| Spectral type | B1.5 III[4] |
| U−B color index | –0.88[2] |
| B−V color index | –0.20[2] |
| Variable type | β Cep[3] |
| Astrometry | |
| Radial velocity (Rv) | +5.4 ± 0.6[5] km/s |
| Proper motion (μ) | RA: −20.94[1] mas/yr Dec.: −23.67[1] mas/yr |
| Parallax (π) | 7.02 ± 0.17 mas[1] |
| Distance | 460 ± 10 ly (142 ± 3 pc) |
| Absolute magnitude (MV) | −4.3[6] |
| Details | |
| Mass | 10.1 ± 1.0[7] M☉ |
| Radius | 7.46 ± 0.17[8][a] R☉ |
| Luminosity | 18,200+860 −820[8] L☉ |
| Surface gravity (log g) | 3.46[6] cgs |
| Temperature | 24,550[8] K |
| Metallicity [Fe/H] | 0.04[9] dex |
| Rotational velocity (v sin i) | 9.5[8] km/s |
| Age | 16–20[5] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alpha Lupi is a giant star with a stellar classification of B1.5 III.[4] It has about ten times the mass of the Sun[7] yet is radiating 18,000 times the Sun's luminosity. The outer atmosphere has an effective temperature of 24,550 K,[8] which gives it the blue-white glow of a B-type star. In 1956 it was identified as a Beta Cephei variable by Bernard Pagel and colleagues,[14] which means it undergoes periodic changes in luminosity because of pulsations in the atmosphere. The variability period is 0.29585 days,[9] or just over 7 hours, 6 minutes. The magnitude varies by about 0.05 magnitudes, or about 5% of its brightness. A 14th magnitude star situated 26" from Alpha Lupi is listed as a companion in double star catalogues.[15]
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.[6] 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.[5]
Visible from the Southern Hemisphere for much of the year, it can also be viewed for a shorter season from the northern tropics and from parts of the northern subtropical latitudes.
α Lupi (Latinised to Alpha Lupi) is the star's Bayer designation.
In Chinese, Kekouan 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.[16] Consequently, the Chinese name for α Lupi itself is 騎官十 (Qí Guān shí, English: the Tenth Star of Imperial Guards.).[17]
R. H. Allen described this star as having the Chinese name Yang Mun or Men (南門), meaning "the South Gate", in his work Star-Names and their Meanings.[18] In Chinese astronomy, 南門 is located in Horn mansion and consisted of α and ε Centauri. It was referred to as Yang Mun, meaning "the south Gate". Allen also suggested that the Babylonian name for the star was "Kakkab Su-gub Gud-Elim" (Star Left Hand of the Horned Bull).[18]
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