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Shaula is λ star in the tail of the "Scorpion". |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Scorpius |
| Right ascension | 17h 33m 36.520s[1] |
| Declination | -37° 06′ 13.76″[1] |
| Apparent magnitude (V) | 1.62 / 14.9 / 12.0 [1][2] |
| Characteristics | |
| Spectral type | B1.5-2 IV+ (A) |
| U−B color index | -0.91 (A) |
| B−V color index | -0.23 (A) |
| Variable type | Beta Cephei (A) |
| Astrometry | |
| Radial velocity (Rv) | -3 km/s |
| Proper motion (μ) | RA: -8.90 mas/yr Dec.: -29.95 mas/yr |
| Parallax (π) | 4.64 ± 0.90 mas |
| Distance | approx. 700 ly (approx. 220 pc) |
| Absolute magnitude (MV) | -5 |
| Other designations | |
| Data sources: | |
| CCDM (2002), Simbad |
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Lambda Scorpii (λ Sco, λ Scorpii) is the second brightest star system in the constellation Scorpius, and one of the brightest stars in the nighttime sky. It has the Bayer designation λ despite being the second brightest in its constellation. It has the traditional name Shaula, which comes from the Arabic الشولاء al-šawlā´ meaning the raised [tail], as it is found in the tail of the scorpion (Scorpius). It is known as 尾宿八 (the Eighth Star of the Tail) in Chinese.
Lambda Scorpii is a multiple star with three visible components. The first, Lambda Scorpii A, is classified as a B-type subgiant. The 15th magnitude Lambda Scorpii B has a separation of 42 arcseconds from component A, while the 12th magnitude Lambda Scorpii C is 95 arcseconds from A. It is not known whether or not these components are physically associated with component A. If they both were, B would be approximately 7500 Astronomical Units and C approximately 17,000 AU (0.27 light years) from A.
Spectroscopic and interferometric observations have shown that A is actually a triple system consisting of two B-type stars and a pre–main sequence star. The primary star is also a beta Cephei variable star.[3] [4] The pre–main sequence star has an orbital period of 6 days and the B companion has a period of 1053 days. The three stars lie in the same orbital plane, strongly suggesting that they were formed at the same time. The masses of the primary, pre–main sequence star and the B companion are 10.4±1.3, 1.8±0.2 and 8.1±1.0 solar masses, respectively. The age of the system is estimated to be in the range 10–13 million years.
The interferometric and spectroscopic observations allow the distance to the system to be determined independently of other methods. Its distance is 112±5 parsecs.
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Together with υ Sco (Lesath), Shaula is listed in MUL.APIN as dSharur4 u dShargaz, meaning "Sharur and Shargaz".[5]
Shaula appears on the flag of Brazil, symbolising the state of Rio Grande do Norte.[6]
USS Shaula (AK-118) was a United States Navy Crater class cargo ship named after the star.
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