Epoch J2000 Equinox J2000
|Right ascension||17h 33m 36.520s|
|Declination||−37° 06′ 13.76″|
|Apparent magnitude (V)||1.62 / 14.9 / 12.0|
|U−B color index||−0.880|
|B−V color index||−0.240|
|Variable type||Beta Cephei (A)|
|Radial velocity (Rv)||−3.00 km/s|
|Proper motion (μ)||RA: −8.90 mas/yr
Dec.: −29.95 mas/yr
|Parallax (π)||5.71 ± 0.90 mas|
|Distance||approx. 570 ly
(approx. 180 pc)
|Absolute magnitude (MV)||−3.70|
|λ Sco A|
|Surface gravity (log g)||3.8 cgs|
|Rotational velocity (v sin i)||150 km/s|
|λ Sco B|
|Surface gravity (log g)||4.0 cgs|
Lambda Scorpii (λ Sco, λ Scorpii) is a blue star and 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 Wei Xiu Ba 尾宿八 (the Eighth Star of the Tail) in Chinese.
Lambda Scorpii is located some 570 light years away from Earth. 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 a beta Cephei variable star with rapid brightness changes of about a hundredth of a magnitude. 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 14.5, 2.0 and 10.6 solar masses, respectively. The age of the system is estimated to be in the range 10–13 million years.
A 15th magnitude star has a separation of 42 arcseconds, whereas a 12th magnitude star is 95 arcseconds away. It is not known whether or not these components are physically associated with Lambda Scorpii. If they both were, the first would have a projected linear separation of approximately 7500 Astronomical units (AU) and the second approximately 17,000 AU (0.27 light years) away.
- Together with Upsilon Scorpii (Lesath), Shaula is listed in MUL.APIN as dSharur4 u dShargaz, meaning "Sharur and Shargaz". In Coptic, they were called Minamref
- Shaula appears on the flag of Brazil, symbolising the state of Rio Grande do Norte.
- The indigenous Boorong people of northwestern Victoria named it as Karik Karik (together with Upsilon Scorpii)., "the Falcons"
- USS Shaula (AK-118) was a United States Navy Crater class cargo ship named after the star.
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- Uytterhoeven, K.; Willems, B.; Lefever, K.; Aerts, C.; Telting, J. H.; Kolb, U. (2004). "Interpretation of the variability of the β Cephei star λ Scorpii". Astronomy and Astrophysics 427 (2): 581–592. Bibcode:2004A&A...427..581U. doi:10.1051/0004-6361:20041223.
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- Rogers, J. H. (February 1998). "Origins of the ancient constellations: I. The Mesopotamian traditions". Journal of the British Astronomical Association, no.1 108: 9–28. Bibcode:1998JBAA..108....9R.
- p. 1678, Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Volume 3, Robert Burnham, New York, Dover Publication, Inc, 1978.
- "Astronomy of the Brazilian Flag". FOTW Flags Of The World website.
- Hamacher, Duane W.; Frew, David J. (2010). "An Aboriginal Australian Record of the Great Eruption of Eta Carinae". Journal of Astronomical History and Heritage 13 (3): 220–34. arXiv:1010.4610. Bibcode:2010JAHH...13..220H.
- Stanbridge, William Edward (1857). "On the astronomy and mythology of the Aborigines of Victoria". Proceedings of the Philosophical Institute of Victoria 2: 137. Bibcode:1857PPIVT...2..137S.