Zeta2 Scorpii
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 54m 35.00503s |
| Declination | −42° 21′ 40.7370″ |
| Apparent magnitude (V) | 3.59 to 3.65 |
| Characteristics | |
| Spectral type | K4 III |
| U−B color index | +1.65 |
| B−V color index | +1.37 |
| R−I color index | +0.68 |
| Astrometry | |
| Radial velocity (Rv) | −18.70±0.06 km/s |
| Proper motion (μ) | RA: −126.721 mas/yr Dec.: −228.837 mas/yr |
| Parallax (π) | 24.2353±0.1985 mas |
| Distance | 135 ± 1 ly (41.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 0.30±0.09 |
| Details | |
| Mass | 1.18±0.15 M☉ |
| Radius | 18.7±1.0 R☉ |
| Luminosity | 130±20 L☉ |
| Surface gravity (log g) | 2.10±0.07 cgs |
| Temperature | 4,286±49 K |
| Metallicity [Fe/H] | −0.10±0.11 dex |
| Rotational velocity (v sin i) | 2.30±0.45 km/s |
| Age | 6.0±2.6 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 | |
| Database references | |
| SIMBAD | data |
Zeta2 Scorpii (Zeta2 Sco, ζ2 Scorpii, ζ2 Sco) is a star in the constellation of Scorpius. With an apparent visual magnitude variying s between 3.59 and 3.65, this star is visible to the naked eye. Parallax measurements derive a distance of 135 light-years to the star.
The spectrum of this star matches a spectral class of K4 III, with the luminosity class "III" classifying it as a giant star that has exhausted all the hydrogen at its core and has expanded. Around six billion years old, this 1.18-solar mass star has swollen to 18.7 solar diameters and now radiates 130 times the Sun's luminosity from its photosphere. The effective temperature of the star has cooled to 4,286 K, giving it the orangish hue typical of a K-type star.
Zeta2 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). ζ2 can also be distinguished from its optical partner, ζ1, because of its orangish colour especially in long-exposure astrophotographs.