Tau Boötis
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 13h 47m 15.7382s |
| Declination | +17° 27′ 24.810″ |
| Apparent magnitude (V) | 4.50 (4.46 to 4.52) |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | F6V + M2 |
| B−V color index | 0.48 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | −16.03±0.15 km/s |
| Proper motion (μ) | RA: −468.923(95) mas/yr Dec.: +63.469(74) mas/yr |
| Parallax (π) | 64.0470±0.1093 mas |
| Distance | 50.92 ± 0.09 ly (15.61 ± 0.03 pc) |
| Absolute magnitude (MV) | 3.38 |
| Orbit | |
| Primary | τ Boo A |
| Companion | τ Boo B |
| Period (P) | 2,420+2,587 −947 yr |
| Semi-major axis (a) | 14.1+8.8 −3.9″ |
| Eccentricity (e) | 0.87±0.04 |
| Inclination (i) | 47.2+2.7 −3.7° |
| Longitude of the node (Ω) | 191.8+3.3 −4.7° |
| Argument of periastron (ω) (secondary) | 290.7+13 −10° |
| Details | |
| τ Boo A | |
| Mass | 1.35±0.03 M☉ |
| Radius | 1.42±0.02 R☉ |
| Luminosity | 3.06±0.16 L☉ |
| Surface gravity (log g) | 4.26±0.06 cgs |
| Temperature | 6,387±44 K |
| Metallicity [Fe/H] | 0.25±0.03 dex |
| Rotation | 3.2±0.2 days |
| Rotational velocity (v sin i) | 14.27±0.06 km/s |
| Age | 1.3+0.4 −0.6 Gyr |
| τ Boo B | |
| Mass | 0.49±0.02 M☉ |
| Radius | 0.48±0.05 R☉ |
| Surface gravity (log g) | 4.90 cgs |
| Temperature | 3,580±90 K |
| Metallicity [Fe/H] | +0.21 dex |
| Rotational velocity (v sin i) | 5.0 km/s |
| Other designations | |
| τ Boo, 4 Boötis, NSV 6444, BD+18°2782, FK5 507, GC 18637, GJ 527, HD 120136, HIP 67275, HR 5185, SAO 100706, ADS 9025, CCDM 13473+1727, WDS J13473+1727A, LTT 14021 | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
Tau Boötis is a wide binary star system in the northern constellation of Boötes. Its name is a Bayer designation that is Latinised from τ Boötis, and abbreviated Tau Boo or τ Boo. This system is visible to the naked eye at a point of light with a combined apparent visual magnitude of 4.50. Based on parallax measurements, It is located at a distance of approximately 51 light-years (16 pc) from the Earth. This system is drifting closer to the Sun with a radial velocity of −16 km/s.
The primary component is an ordinary F-type main-sequence star that is larger, brighter, and more massive than the Sun, while the secondary is a faint red dwarf. In 1999, an extrasolar planet was detected orbiting the primary star.