Zeta2 Scorpii

ζ² Scorpii

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Scorpius
Right ascension	16^h 54^m 35.0053^s[1]
Declination	−42° 21′ 40.726″[1]
Apparent magnitude (V)	3.59 to 3.65[2]
Characteristics
Spectral type	K4III[1]
U−B color index	+1.65[3]
B−V color index	+1.37[3]
R−I color index	+0.68[3]
Astrometry
Radial velocity (Rv)	−18.7 ± 0.9[1] km/s
Proper motion (μ)	RA: −126.55[1] mas/yr Dec.: −227.77[1] mas/yr
Parallax (π)	21.67 ± 0.85[1] mas
Distance	151 ± 6 ly (46 ± 2 pc)
Absolute magnitude (MV)	0.30 ± 0.09[4]
Details
Mass	1.19 ± 0.14[4] M☉
Radius	21.0 ± 1.6[4] R☉
Surface gravity (log g)	1.84 ± 0.10[4] cgs
Temperature	4,169[4] K
Metallicity [Fe/H]	+0.06[4] dex
Age	5.80 ± 2.26[4] 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.[1]
Database references
SIMBAD	data

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

Zeta² Scorpii (Zeta² Sco, ζ² Scorpii, ζ² Sco) is a K-type orange giant star in the constellation of Scorpius.^[1] 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 our 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 151 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.

References

1. NSV 8028 -- Variable Star, database entry, SIMBAD. Accessed on line November 20, 2009.
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. 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.
4. 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