Tau Orionis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 17m 36.38856s |
| Declination | −06° 50′ 39.8702″ |
| Apparent magnitude (V) | 3.58 |
| Characteristics | |
| Spectral type | B5 III |
| U−B color index | −0.47 |
| B−V color index | −0.11 |
| Astrometry | |
| Radial velocity (Rv) | +20.1 km/s |
| Proper motion (μ) | RA: −17.61 mas/yr Dec.: −9.24 mas/yr |
| Parallax (π) | 6.60±0.15 mas |
| Distance | 490 ± 10 ly (152 ± 3 pc) |
| Orbit | |
| Period (P) | 90.29 days |
| Eccentricity (e) | 0.834 |
| Longitude of the node (Ω) | 156° |
| Details | |
| A | |
| Mass | 6.6 M☉ |
| B | |
| Mass | 5.3 M☉ |
| Other designations | |
| τ Ori, 20 Orionis, BD−07°1028, HD 34503, HIP 24674, HR 1735, SAO 131952. | |
| Database references | |
| SIMBAD | data |
Tau Orionis (τ Ori, τ Orionis) is a binary star in the constellation Orion. If an imaginary line is drawn north-west between the stars Rigel and Mintaka, Tau Orionis can be found roughly one-sixth of the way to Mintaka. It is visible to the naked eye with a combined apparent visual magnitude of 3.58. Based upon an annual parallax shift of 6.6 mas, it is located around 490 light years distant.
This is a spectroscopic binary system with an orbital period of 90 days and a very high eccentricity of 0.834. It is a heartbeat star, showing variations on its apparent magnitude during to the close periastron passage. The components have masses of 6.6 and 5.3 M☉ and a combined stellar classification of B5 III. The star has a peculiar velocity through space of 16.9 km/s.
Tau Orionis has three visual companions: magnitude 11.0 component B at an angular separation of 33.30″ along a position angle of 251°; magnitude 10.9 component C lying some 3.80″ from component B; and magnitude 10.9 component D at 36.0″ from τ Ori along a position angle of 51°, all as of 2011.