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 about 6,000 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 135 light-years 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 astrophotographs.

ζ² Scorpii

Reddish ζ2 Scorpii alongside the fainter ζ1 Scorpii to the south of NGC 6231
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Scorpius
Right ascension	16h 54m 35.00503s[1]
Declination	−42° 21′ 40.7370″[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: −126.721 mas/yr[1] Dec.: −228.837 mas/yr[1]
Parallax (π)	24.2353 ± 0.1985 mas[1]
Distance	135 ± 1 ly (41.3 ± 0.3 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
ζ2 Sco, Zeta2 Scorpii, Zeta2 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