Omega2 Scorpii

ω² Scorpii
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Scorpius
Right ascension	16h 07m 24.32818s
Declination	−20° 52′ 07.5518″
Apparent magnitude (V)	+4.320
Characteristics
Evolutionary stage	horizontal branch
Spectral type	G6/8III
U−B color index	+0.494
B−V color index	+0.850
Astrometry
Radial velocity (Rv)	−5.4 km/s
Proper motion (μ)	RA: +44.81 mas/yr ; Dec.: −45.42 mas/yr
Parallax (π)	11.22±0.32 mas
Distance	291 ± 8 ly ; (89 ± 3 pc)
Absolute magnitude (MV)	−0.62
Details
Mass	3.27 M☉
Radius	15.0 R☉
Luminosity	163 L☉
Surface gravity (log g)	2.62±0.11 cgs
Temperature	5,363±42 K
Metallicity [Fe/H]	+0.03±0.05 dex
Age	282 Myr
Other designations
	Jabhat al Akrab, ω2 Sco, 10 Scorpii, BD−20°4408, HD 144608, HIP 78990, HR 5997, SAO 184135
Database references
SIMBAD	data

ω² Scorpii, Latinised as Omega² Scorpii, is a suspected^[11] variable star in the zodiac constellation of Scorpius. A component of the visual double star ω Scorpii, it is bright enough to be seen with the naked eye having an apparent visual magnitude of +4.320.^[2] The distance to this star, as determined using parallax measurements,^[1] is around 291 light years. The visual magnitude of this star is reduced by 0.38 because of extinction from interstellar dust.^[6]

It is 0.05 degree north of the ecliptic, so can be occulted by the moon and planets.

This is a G-type giant star with a stellar classification of G6/8III.^[4] With an estimated age of 282 million years,^[6] it is an evolved, thin disk star that is currently on the red horizontal branch.^[3] The interferometry-measured angular diameter of this star is 1.63 ± 0.10 mas,^[12] which, at its estimated distance, equates to a physical radius of nearly 16 times the radius of the Sun.^[13] It has 3.27 times the mass of the Sun,^[6] and radiates 141 times the Sun's luminosity^[14] The effective temperature of the star's outer atmosphere is 5,363 K.^[8]

Names

In the Cook Islands, a traditional story is told of twins who flee their parents into the sky and become the pair of stars Omega² and Omega¹ Scorpii. The girl, who is called Piri-ere-ua "Inseparable", keeps tight hold of her brother, who is not named.^[15] (The IAU used a version of this story from Tahiti to name Mu² Scorpii.)

References

^ ^a ^b ^c ^d ^e ^f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
^ ^a ^b ^c ^d Kozok, J. R. (September 1985), "Photometric observations of emission B-stars in the southern Milky Way", Astronomy and Astrophysics Supplement Series, 61: 387–405, Bibcode:1985A&AS...61..387K.
^ ^a ^b Afşar, M.; et al. (July 2012), "Chemical Compositions of Thin-disk, High-metallicity Red Horizontal-branch Field Stars", The Astronomical Journal, 144 (1): 20, arXiv:1205.3659, Bibcode:2012AJ....144...20A, doi:10.1088/0004-6256/144/1/20, S2CID 119249237, 20.
^ ^a ^b Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Declinations -26°.0 to -12°.0, vol. 4, Bibcode:1988mcts.book.....H.
^ Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W.
^ ^a ^b ^c ^d ^e ^f Takeda, Yoichi; et al. (August 2008), "Stellar Parameters and Elemental Abundances of Late-G Giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781, S2CID 16258166.
^ ^a ^b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d Prugniel, P.; et al. (2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID 54940439.
^ Allen, Richard Hinckley (1963) [1899], Star Names: Their Lore and Meaning (Revised ed.), New York: Dover Publications, p. 367, ISBN 0-486-21079-0. {{citation}}: ISBN / Date incompatibility (help)
^ "* ome02 Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-25.
^ Sterken, C. (January 1977), "uvby Photometry of the Suspected Variable omega2 Sco", Information Bulletin on Variable Stars, 1230: 1, Bibcode:1977IBVS.1230....1S.
^ Richichi, A.; Percheron, I. (May 2002), "CHARM: A Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 386 (2): 492–503, Bibcode:2002A&A...386..492R, CiteSeerX 10.1.1.170.2863, doi:10.1051/0004-6361:20020236.
^ Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1.. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(89\cdot 1.63\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 31.2\cdot R_{\bigodot }\end{aligned}}$
^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
^ Johannes Carl Andersen (1931) Myths and Legends of the Polynesians. 1995 Dover reprint, p.399–400.