Tau Ophiuchi (τ Oph) is a multiple star in the constellation Ophiuchus, approximately 167 light years away based on parallax.[1] Its two main components are two yellow-white main sequence stars, A, of magnitude 5.24 and class F2V, and B, of magnitude 5.94 and class F5V,[2] orbiting each other with a period of 257 years and eccentricity around 0.77.[7] A is reported as a spectroscopic binary with a smaller star of 0.29 solar masses orbiting it every 186 days.[5] An additional component, C, has a separation of 100.8" and magnitude 11.28.[8]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 18h 03m 04.91992s[1] |
| Declination | −8° 10′ 49.2586″[1] |
| Apparent magnitude (V) | 5.24 (A) / 5.94 (B) [2] |
| Characteristics | |
| Spectral type | F2V(A) / F5V (B) [2] |
| U−B color index | +0.05 (A)[3] |
| B−V color index | +0.38 (A)[3] |
| Astrometry | |
| Radial velocity (Rv) | -38.39[4] km/s |
| Proper motion (μ) | RA: +15.78[1] mas/yr Dec.: -37.79[1] mas/yr |
| Parallax (π) | 19.48 ± 0.66 mas[1] |
| Distance | 167 ± 6 ly (51 ± 2 pc) |
| Details | |
| Mass | 1.54 (A) / 1.29 (B)[5] M☉ |
| Surface gravity (log g) | 4.18 (A)[6] cgs |
| Temperature | 6,813 (A)[6] K |
| Other designations | |
| Database references | |
| SIMBAD | data |