Epsilon Scorpii

ε Scorpii

Location of ε Sco (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Scorpius
Right ascension	16h 50m 09.8s[1]
Declination	−34° 17′ 36″[1]
Apparent magnitude (V)	2.24 - 2.35[2]
Characteristics
Evolutionary stage	red clump[3]
Spectral type	K1 III[4]
U−B color index	+1.147[5]
B−V color index	+1.150[5]
Variable type	suspected[2]
Astrometry
Radial velocity (Rv)	−2.5[6] km/s
Proper motion (μ)	RA: −614.85[1] mas/yr Dec.: −255.98[1] mas/yr
Parallax (π)	51.19±0.22 mas[1]
Distance	63.7 ± 0.3 ly (19.54 ± 0.08 pc)
Absolute magnitude (MV)	0.78±0.04[7]
Details
Mass	1.31[8] M☉
Radius	11.6[9] R☉
Luminosity	60[8] L☉
Surface gravity (log g)	2.34[8] cgs
Temperature	4,560[10] K
Metallicity [Fe/H]	−0.17[10] dex
Rotational velocity (v sin i)	2.6±0.5[11] km/s
Age	3.92[8] Gyr
Other designations
Wei, Larawag, 26 Scorpii, CD−34 11285, FK5 628, GCTP 3823.00, Gl 639.1, GJ 9579, HD 151680, HIP 82396, HR 6241, LHS 3244, SAO 208078[12]
Database references
SIMBAD	data

Epsilon Scorpii (ε Scorpii, abbreviated Eps Sco, ε Sco), formally named Larawag /ˈlærəwæɡ/,^[13] is a star in the southern zodiac constellation of Scorpius. It has an apparent visual magnitude of +2.3,^[5] making it the fifth-brightest member of the constellation. Parallax measurements made during the Hipparcos mission provide an estimated distance to this star of around 63.7 light-years (19.5 parsecs) from the Sun.^[1]

Epsilon Scorpii has a stellar classification of K1 III,^[4] which indicates it has exhausted the supply of hydrogen at its core and evolved into a giant star. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 5.99±0.06 mas,^[14] which, at its estimated distance, equates to a physical radius of nearly 12 times the radius of the Sun. Presently it is generating energy through the nuclear fusion of helium at its core, which, considering the star's composition, places it along an evolutionary branch termed the red clump.^[3] The star's outer atmosphere has an effective temperature of 4,560 K,^[10] giving it the orange hue of a cool K-type star.

ε Scorpii is classified as a suspected variable star,^[2] although a study of Hipparcos photometry showed a variation of no more than 0.01–0.02 magnitudes.^[3] It is an X-ray source with a luminosity of (1.5–1.6)×10²⁷ erg/s.^[7][15]

ε Scorpii (Latinised to Epsilon Scorpii) is the star's Bayer designation.

The star bore the traditional name Larawag in the culture of the Wardaman people of the Northern territory of Australia,^[16] meaning clear sighting.^[17] In 2016, the IAU organized a Working Group on Star Names (WGSN)^[18] to catalog and standardize proper names for stars. The WGSN approved the name Larawag for Epsilon Scorpii on 19 November 2017 and it is now so included in the List of IAU-approved Star Names.^[13]

Patrick Moore introduced the name Wei as Chinese name for this star.^[19] However, this seems to be a misreading, as Chinese 尾宿 (Wěi Xiù, English Tail) refers to an asterism (i.e. Chinese constellation) consisting of Epsilon Scorpii, Mu¹ Scorpii, Zeta¹ Scorpii and Zeta² Scorpii, Eta Scorpii, Theta Scorpii, Iota² Scorpii and Iota¹ Scorpii, Kappa Scorpii, Lambda Scorpii and Upsilon Scorpii.^[20] Consequently, the name for Epsilon Scorpii itself is 尾宿二 (Wěi Xiù èr), which means "the Second Star of Tail".^[21][22]

Epsilon Scorpii appears on the flag of Brazil, symbolising the state of Ceará.^[23]