Back النياط سيغما Arabic Al Niyat AST Sigma de l'Escorpió Catalan Alniyat German Al Niyat Spanish سیگما کژدم Persian Sigma Scorpii French סיגמא בעקרב HE Sigma Scorpii Italian さそり座シグマ星 Japanese

Sigma Scorpii

"Al Niyat" redirects here. For the other star that traditionally bore this name, see Tau Scorpii.
Sigma Scorpii
Location of σ Scorpii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Scorpius
Right ascension 16h 21m 11.31571s[1]
Declination −25° 35′ 34.0515″[1]
Apparent magnitude (V) +2.88[2]
Characteristics
Spectral type B1 III[3] + B1 V[4]
U−B color index −0.70[2]
B−V color index +0.13[2]
Astrometry
Radial velocity (Rv)−0.4[5] km/s
Proper motion (μ) RA: −10.60[1] mas/yr
Dec.: −16.28[1] mas/yr
Distance568+75
−59 ly
(174+23
−18[4] pc)
Absolute magnitude (MV)−4.12±0.34 / −3.32±0.34[4]
Orbit[4]
Primaryσ Sco Aa1
Companionσ Sco Aa2
Period (P)33.010±0.002 days
Semi-major axis (a)3.62±0.06 mas
Eccentricity (e)0.3220±0.0012
Inclination (i)158.2±2.3°
Longitude of the node (Ω)104±5°
Periastron epoch (T)34889.0±1.0 MJD
Argument of periastron (ω)
(secondary)		283±5°
Details
σ Sco Aa1
Mass18.4±5.4,[4] 17.2-18.0[6] M☉
Radius12.7±1.8[4] R☉
Luminosity29,000±8,000,[4] 95,500[6] L☉
Surface gravity (log g)3.85[4] cgs
Temperature26,150±1,070,[4] 27,700[6] K
Metallicity [Fe/H]−0.20±0.20[7] dex
Rotational velocity (v sin i)25[8] km/s
Age8.0±0.2,[9] 8-10[6] Myr
σ Sco Aa2
Mass11.9±3.1[4] M☉
Radius11[4] R☉
Luminosity16000±4000[4] L☉
Other designations
Alniyat, Al Niyat, Pekehāwani, 20 Scorpii, ADS 10009, CD-25 11485, FK5 607, HD 147165, HIP 80112, HR 6084, SAO 184336, WDS 16212-2536.[10]
Database references
SIMBADdata

Sigma Scorpii (or σ Scorpii, abbreviated Sigma Sco or σ Sco), is a multiple star system in the constellation of Scorpius, located near the red supergiant Antares, which outshines it. This system has a combined apparent visual magnitude of +2.88,[2] making it one of the brighter members of the constellation. Based upon parallax measurements made during the Hipparcos mission, the distance to Sigma Scorpii is roughly 696 light-years (214 parsecs).[1] North et al. (2007) computed a more accurate estimate of 568+75
−59 light years (174+23
−18 parsecs).[4]

The system consists of a spectroscopic binary with components designated Sigma Scorpii Aa1 (officially named Alniyat /ælˈnaɪjæt/, the traditional name for the entire star system)[11][12] and a Beta Cephei variable) and Aa2; a third component (designated Sigma Scorpii Ab) at 0.4 arcseconds from the spectroscopic pair, and a fourth component (Sigma Scorpii B) at about 20 arcseconds.[13]

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  12. ^ Cite error: The named reference IAU-LSN was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference WDS was invoked but never defined (see the help page).
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