Zeta² Scorpii

Zeta² Scorpii (Zeta² Sco, ζ² Scorpii, ζ² Sco) is a K-type orange giant star in the constellation of Scorpius.[8] It has an apparent visual magnitude which varies between 3.59 and 3.65,[2] and is located near the blue-white supergiant star ζ¹ Scorpii in Earth's sky. In astronomical terms, ζ² is much closer to the Sun and unrelated to ζ¹ except for line-of sight co-incidence. ζ¹ is 5,700 light-years away and probably an outlying member of open star cluster NGC 6231 (also known as the "northern jewel box" cluster), whereas ζ² is a mere 132 lightyears distant and thus much less luminous in real terms. ζ² can also be distinguished from its optical partner, ζ¹, because of its orangish colour especially in long-exposure astrophographs.

For other stars with this Bayer designation, see Zeta Scorpii.

ζ² Scorpii

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Scorpius
Right ascension	16^h 54^m 35.00435^s[1]
Declination	−42° 21′ 40.7407″[1]
Apparent magnitude (V)	3.59 to 3.65[2]
Characteristics
Spectral type	K4 III[3]
U−B color index	+1.65[4]
B−V color index	+1.37[4]
R−I color index	+0.68[4]
Astrometry
Radial velocity (Rv)	−18.7±0.9[5] km/s
Proper motion (μ)	RA: −127.72[1] mas/yr Dec.: −229.44[1] mas/yr
Parallax (π)	24.65 ± 0.27[1] mas
Distance	132 ± 1 ly (40.6 ± 0.4 pc)
Absolute magnitude (MV)	0.30±0.09[6]
Details
Mass	1.19±0.14[6] M☉
Radius	21.0±1.6[6] R☉
Surface gravity (log g)	1.84±0.10[6] cgs
Temperature	4,169[6] K
Metallicity [Fe/H]	+0.06[6] dex
Rotational velocity (v sin i)	2.30[7] km/s
Age	5.80±2.26[6] Gyr
Other designations
ζ^2 Sco, Zeta^2 Scorpii, Zeta^2 Sco, CD−42 11646, CPD−42 7549, GC 22751, HD 152334, HIP 82729, HR 6271, LTT 6737, NLTT 43744, PPM 322371, SAO 227402.[8]
Database references
SIMBAD	data

Reddish ζ² Scorpii alongside the fainter ζ¹ Scorpii to the south of NGC 6231

References

1. van Leeuwen, F. (November 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.
2. NSV 8028, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 20, 2009.
3. Landi Dessy, J.; Keenan, P. C. (November 1966), "Spectral Types on the MK System for Forty-Three Bright Southern Stars, K2-M6", Astrophysical Journal, 146: 587, Bibcode:1966ApJ...146..587L, doi:10.1086/148925.
4. HR 6271, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line November 20, 2009.
5. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
6. da Silva, L.; et al. (November 2006), "Basic physical parameters of a selected sample of evolved stars", Astronomy and Astrophysics, 458 (2): 609–623, arXiv:astro-ph/0608160, Bibcode:2006A&A...458..609D, doi:10.1051/0004-6361:20065105.
7. Jofré, E.; Petrucci, R.; Saffe, C.; Saker, L.; de la Villarmois, E. Artur; Chavero, C.; Gómez, M.; Mauas, P. J. D. (2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574, arXiv:1410.6422, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474, A50.
8. "zet02 Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-20.