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λ Scorpii
	Location of λ Scorpii (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Scorpius
Pronunciation	/ˈʃɔːlə/
Right ascension	17h 33m 36.520s
Declination	−37° 06′ 13.76″
Apparent magnitude (V)	1.62 + 14.9 + 12.0
Characteristics
Spectral type	B1.5IV + B2IV
U−B color index	−0.880
B−V color index	−0.240
Variable type	Beta Cephei (A)
Astrometry
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
Orbit
Primary	A
Companion	B
Period (P)	2.8825 yr
Semi-major axis (a)	49.3 mas
Eccentricity (e)	0.121
Inclination (i)	77.2°
Orbit
Primary	Aa
Companion	Ab
Period (P)	5.9520 d
Eccentricity (e)	0.26
Semi-amplitude (K1); (primary)	39.3 km/s
Details
λ Sco Aa
Mass	10.4 M☉
Radius	8.8±1.2 R☉
Luminosity	36,300 L☉
Surface gravity (log g)	3.8 cgs
Temperature	25,000±1,000 K
Rotation	3.4±0.5 d
Rotational velocity (v sin i)	150 km/s
λ Sco B
Mass	8.1 M☉
Radius	4.7±1.0 R☉
Surface gravity (log g)	4.0 cgs
Temperature	25,000±1,000 K
λ Sco Ab
Mass	1.8 M☉
Other designations
	Shaula, 35 Scorpii, 35 Sco, CD−37 11673, FK5 652, HD 158926, HIP 85927, HR 6527, SAO 208954, CCDM J17336-3706A/B/C
Database references
SIMBAD	data

Lambda Scorpii is a triple star system and the second-brightest object in the constellation of Scorpius. It is formally named Shaula; Lambda Scorpii is its Bayer designation, which is Latinised from λ Scorpii and abbreviated Lambda Sco or λ Sco. With an apparent visual magnitude of 1.62, it is one of the brightest stars in the night sky.

Nomenclature

λ Scorpii (Latinised to Lambda Scorpii) is the star system's Bayer designation.

It bore the traditional name Shaula, which comes from the Arabic الشولاء al-šawlā´ meaning 'the raised [tail]', as it is found in the tail of Scorpius, the scorpion. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[12] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016^[13] included a table of the first two batches of names approved by the WGSN, which included Shaula for the star λ Scorpii Aa.

In Indian Astronomy it is called MulA Nakshathram. Mūla ("root") (Devanagari मूल/मूळ) (Tamil: மூலம்) is the 19th nakshatra or "lunar mansion" in Vedic astrology. The symbol of Mula is a bunch of roots tied together (reticulated roots) or an 'elephant goad' (ankusha).^{[citation needed]}

In Chinese, 尾宿 (Wěi Xiù), meaning Tail, refers to an asterism consisting of λ Scorpii, ε Scorpii, ζ¹ Scorpii, ζ² Scorpii, η Scorpii, θ Scorpii, ι¹ Scorpii, ι² Scorpii, κ Scorpii, μ¹ Scorpii, and υ Scorpii.^[14] Consequently, the Chinese name for λ Scorpii itself is 尾宿八 (Wěi Xiù bā), "the Eighth Star of Tail".^[15]

Together with υ Scorpii (Lesath), Shaula is listed in the Babylonian compendium MUL.APIN as ^dSharur₄ u ^dShargaz, meaning "Sharur and Shargaz".^[16]

In Coptic, they were called Minamref.^[17]

The indigenous Boorong people of northwestern Victoria (Australia) named it (together with Upsilon Scorpii) Karik Karik,^[18] "the Falcons".^[19]

Properties

A light curve for Lambda Scorpii, plotted from *TESS* data.^[20] The large dips in brightness are eclipses, and the rapid oscillations show the Beta Cephei variability.

Lambda Scorpii is located some 570 light-years away from the Sun.

Spectroscopic and interferometric observations have shown that it is actually a triple star system consisting of two B-type stars and a pre-main-sequence star.^[8] The primary star is a Beta Cephei variable star with rapid brightness changes of about a hundredth of a magnitude.^[6]^[5] 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 7,500 astronomical units (AU) and the second approximately 17,000 AU (0.27 light-years) away. Gaia Data Release 3 reports that the fainter of these two stars is a little larger and brighter than the sun and about 420 light years away,^[21] while the brighter star is a luminous background object.^[22]