Eta Ophiuchi
| 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 | |
| Evolutionary stage | main sequence |
| Spectral type | A2V + A2V |
| 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) | 87.77+0.28 −0.24 yr |
| Semi-major axis (a) | 31.05+1.41 −1.35 au |
| Eccentricity (e) | 0.93077+0.00013 −0.00012 |
| Inclination (i) | 96.305+0.019 −0.018° |
| Longitude of the node (Ω) | 39.241±0.011° |
| Periastron epoch (T) | 2024.526 |
| Argument of periastron (ω) (secondary) | 275.90+0.10 −0.11° |
| Details | |
| η Oph A (Sabik) | |
| Mass | 2.25+0.18 −0.09 M☉ |
| Radius | 2.5±0.4 R☉ |
| Luminosity | 35 L☉ |
| Surface gravity (log g) | 3.74 cgs |
| Temperature | 9,000+1,250 −750 K |
| Metallicity | −0.01 dex |
| Rotational velocity (v sin i) | 23 km/s |
| Age | 500+210 −280 Myr |
| η Oph B | |
| Mass | 2.03±0.02 M☉ |
| Radius | 2.0+0.3 −0.2 R☉ |
| Luminosity | 21 L☉ |
| Temperature | 8,700±450 K |
| Age | 500+210 −280 Myr |
| Other designations | |
| Sabik, 35 Oph, BD−15°4467, GCTP 3895.00, Gl 656.1A/B, HD 155125, HIP 84012, HR 6378, SAO 160332, WDS J17104-1544AB | |
| Database references | |
| SIMBAD | data |
Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. With a combined apparent magnitude of +2.43, it is the second-brightest of the constellation and one of the brightest stars in the night sky. Based on parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years away.
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.