WR 104
 WR 104 |
|
| Observation data Epoch 2000 Equinox 2000 |
|
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 02m 04.07s |
| Declination | −23° 37′ 41.2″ |
| Apparent magnitude (V) | 13.28 (12.7 - 14.6) + 15.36 |
| Characteristics | |
| Spectral type | WC9d/B0.5V |
| Astrometry | |
| Distance | 2,300pc |
| Absolute magnitude (MV) | −5.4 (−4.8 + −4.6) |
| Orbit | |
| Period (P) | 241.5 days |
| Semi-major axis (a) | 2.34 AU |
| Eccentricity (e) | < 0.06 |
| Inclination (i) | < 16° |
| Details | |
| Luminosity | 250,000 L☉ |
| WR | |
| Radius | 10 R☉ |
| Temperature | 40,000 K |
| OB | |
| Radius | 10 R☉ |
| Temperature | 30,000 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Coordinates: 
18h 02m 04.07s, −23° 37′ 41.2″
WR 104 is part of a triple star system located about 7,500 light years from Earth. The primary is a Wolf-Rayet star, abbreviated as WR, with a B0.5 main sequence star in close orbit with another more distant fainter companion.
The WR star is surrounded by a distinctive Wolf–Rayet nebula, often referred to as the Pinwheel Nebula, and is now considered among a new object class of so-called pinwheel nebulae. The rotational axis of the binary system, and likely of the two closest stars, is directed approximately towards Earth. Within the next few hundred thousand years, the Wolf-Rayet star is predicted to probably become a core-collapse-supernova with a small chance of producing a long duration gamma-ray burst.
The Wolf-Rayet star that produces the characteristic emission line spectrum of WR 104 has a resolved companion and an unresolved spectroscopic companion, forming a triple system.
The spectroscopic pair consist of the Wolf-Rayet star and a B0.5 main sequence star. The WR star is visually 0.3 magnitudes fainter than the main sequence star, although the WR star is typically considered the primary as it dominates the appearance of the spectrum and is more luminous. The two are in a nearly circular orbit separated by about 2 AU, which would be about one milli-arcsecond at the assumed distance. The two stars orbit every 241.5 days with a small inclination (i.e. nearly face-on).
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