Theta Muscae
Theta Muscae (θ Muscae) is a multiple star system in the southern constellation Musca ("the Fly"), containing a Wolf-Rayet star and two massive companions. With an apparent magnitude of 5.5, it is the second-brightest Wolf–Rayet star in the sky, although much of the visual brightness comes from the massive companions and it is not one of the closest of its type.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Musca |
| Right ascension | 13h 08m 07.15286s |
| Declination | −65° 18′ 21.6819″ |
| Apparent magnitude (V) | 5.53 (5.662 + 7.555) |
| Characteristics | |
| θ Mus A | |
| Spectral type | WC5/6 + O6/7V + O9.5/B0Iab |
| U−B color index | −0.91 |
| B−V color index | −0.43 |
| Variable type | Eclipsing + WR |
| B | |
| Spectral type | O9III |
| U−B color index | −0.90 |
| B−V color index | −0.055 |
| Astrometry | |
| Radial velocity (Rv) | −28.4 km/s |
| Proper motion (μ) | RA: −2.10 mas/yr Dec.: −11.52 mas/yr |
| Parallax (π) | 0.26 ± 0.48 mas |
| Distance | 7,400 ly (2,270 pc) |
| Absolute magnitude (MV) | −6.2 |
| Orbit | |
| Period (P) | 19.1375 d |
| Eccentricity (e) | 0.00 (assumed) |
| Inclination (i) | 49±6° |
| Semi-amplitude (K1) (primary) | 221±6 km/s |
| Details | |
| WR | |
| Mass | <11.5 M☉ |
| Luminosity | 234,000 L☉ |
| O | |
| Mass | 44 M☉ |
| Luminosity | 295,000 L☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
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