Alpha Lupi
 Location of α Lupi (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Lupus |
| Right ascension | 14h 41m 55.75579s |
| Declination | –47° 23′ 17.5155″ |
| Apparent magnitude (V) | 2.30(2.29 - 2.34) |
| Characteristics | |
| Spectral type | B1.5 III |
| U−B color index | –0.88 |
| B−V color index | –0.20 |
| Variable type | β Cep |
| Astrometry | |
| 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 ± 0.17mas |
| Distance | 460 ± 10 ly (142 ± 3 pc) |
| Absolute magnitude (MV) | −4.3 |
| Details | |
| Mass | 10.1 ± 1.0 M☉ |
| Luminosity | 25,000 L☉ |
| 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 |
| Age | 16–20 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Alpha Lupi (α Lupi, α Lup) is the brightest star in the southern constellation of Lupus. According to the Bortle Dark-Sky Scale, its apparent visual magnitude of 2.3 makes it readily visible to the naked eye even from highly light-polluted locales. 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. It is one of the nearest supernova explosion candidates.
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 by Bernard Pagel and colleagues, 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 0.05, or about 5% of the total luminosity. A 14th magnitude star situated 26" from Alpha Lupi is listed as a companion in double star catalogues, but may just be an optical double.
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.
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