Eta Ophiuchi
Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. Based on parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years from the Sun.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 10m 22.68689s |
| Declination | –15° 43′ 29.6639″ |
| Apparent magnitude (V) | 2.43 (3.05/3.27) |
| Characteristics | |
| Spectral type | A1 IV + A1 IV |
| U−B color index | +0.09 |
| B−V color index | +0.05 |
| Astrometry | |
| Radial velocity (Rv) | –0.9 km/s |
| Proper motion (μ) | RA: +40.13 mas/yr Dec.: +99.17 mas/yr |
| Parallax (π) | 36.91 ± 0.80 mas |
| Distance | 88 ± 2 ly (27.1 ± 0.6 pc) |
| Orbit | |
| Period (P) | 87.58 ± 1.00 yr |
| Semi-major axis (a) | 1.396 ± 0.010″ |
| Eccentricity (e) | 0.950 ± 0.020 |
| Inclination (i) | 95.2 ± 2.0° |
| Longitude of the node (Ω) | 38.9 ± 1.0° |
| Periastron epoch (T) | 2024.68 ± 0.50 |
| Argument of periastron (ω) (secondary) | 274.8 ± 2.0° |
| Details | |
| Metallicity [Fe/H] | −0.01 dex |
| η Oph A | |
| Mass | 2.966 M☉ |
| Rotational velocity (v sin i) | 23 km/s |
| η Oph B | |
| Mass | 3.478 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Ophiuchi is part of a multiple star system designated WDS J17104-1544. It itself is designated WDS J17104-1544AB and its two components WDS J17104-1544A (also called Sabik /ˈseɪbɪk/, the traditional name for the system) and WDS J17104-1544B. The 'C' component is UCAC4 372-080717 and 'D' is UCAC2 26022336.
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