66 Tauri
Star in the constellation Taurus
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66 Tauri, also known as r Tauri, is a binary star in the constellation of Taurus. The combined apparent magnitude of the system is 5.098,[2] with the magnitudes of the two components being 5.8 and 5.9, respectively.[3] Parallax measurements by Hipparcos put 66 Tauri at some 400 light-years (121 parsecs) away.[1]
Right ascension04h 23m 51.82553s[1]
Declination+09° 27′ 39.4939″[1]
Apparentmagnitude(V)5.098[2] (5.8 / 5.9)[3]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 23m 51.82553s[1] |
| Declination | +09° 27′ 39.4939″[1] |
| Apparent magnitude (V) | 5.098[2] (5.8 / 5.9)[3] |
| Characteristics | |
| Spectral type | A3V + A4V[4] |
| U−B color index | +0.10[5] |
| B−V color index | +0.07[5] |
| Astrometry | |
| Radial velocity (Rv) | −8.70±1[6] km/s |
| Proper motion (μ) | RA: −20.32[1] mas/yr Dec.: −5.32[1] mas/yr |
| Parallax (π) | 8.24±0.31 mas[1] |
| Distance | 400 ± 10 ly (121 ± 5 pc) |
| Absolute magnitude (MV) | −0.32[7] |
| Orbit[3] | |
| Period (P) | 54.77 yr |
| Semi-major axis (a) | 0.188″ |
| Eccentricity (e) | 0.720 |
| Inclination (i) | 34.2° |
| Longitude of the node (Ω) | 239.8° |
| Periastron epoch (T) | 1937.24 |
| Argument of periastron (ω) (secondary) | 332.0° |
| Details | |
| 66 Tau A | |
| Mass | 2.89[8][note 1] M☉ |
| Rotational velocity (v sin i) | 81[9] km/s |
| 66 Tau B | |
| Mass | 2.76[8][note 1] M☉ |
| Other designations | |
| r Tau, BD+09°570, HD 27820, HIP 20522, HR 1381, SAO 111791 | |
| Database references | |
| SIMBAD | data |
This is a visual binary where the positions of the two stars are tracked over time, and used to calculate an orbit. The two stars orbit each other every 55 years.[3] Their orbit is fairly eccentric, at 0.720, and the two stars are separated by 0.188″ on average.[3] Both stars are A-type main-sequence stars with similar masses.[8]
Notes
- Cvetkovic et al. gives two possible mass sums: 2.89 / 2.76 M☉ or 2.88 / 2.77 M☉.