Tau Ophiuchi

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]

τ Ophiuchi

Location of τ Ophiuchi (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Ophiuchus
Right ascension	18h 03m 04.91992s[1]
Declination	−08° 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
BD−08°4549, CCDM J18031-0811AB, 69 Ophiuchi, HIP 88404, HD 164764+164765, HR 6733+6734, WDS J18031-0811AB
Database references
SIMBAD	data