| Observation data EpochJ2000.0 EquinoxJ2000.0 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 18m 29.1311s[1] |
| Declination | −13° 13′ 01.514″[1] |
| Apparent magnitude (V) | 11.56[2] |
| Characteristics | |
| Spectral type | WN4-s[3] |
| U−Bcolor index | −0.47[4] |
| B−Vcolor index | +0.28[4] |
| Astrometry | |
| Proper motion (μ) | RA: −3.601[1]mas/yr Dec.: −2.998[1]mas/yr |
| Parallax (π) | 0.2096±0.0268 mas[1] |
| Distance | approx. 16,000 ly (approx. 4,800 pc) |
| Absolute magnitude (MV) | −3.8[5] |
| Details | |
| Mass | 13[3] M☉ |
| Radius | 1.26[3] R☉ |
| Luminosity | 229,000[3] L☉ |
| Temperature | 112,200[3] K |
| Other designations | |
| WR 7,HIP 35378,HD 56925,2MASS J07182912-1313015. | |
| Database references | |
| SIMBAD | data |
WR 7 (HD 56925) is aWolf–Rayet star in the constellation ofCanis Major. It lies at the centre of a complexbubble of gas which is shocked and partially ionised by the star's radiation and winds.
The distance is uncertain, with estimates between 3.5kiloparsecs (11,410light-years) and 6.9 kiloparsecs (22,500 light-years). Assuming a distance of 4.8 kiloparsecs (15,600 light-years), this star is calculated to be 229,000 times brighter than the Sun, 13 times more massive, and 1.26 times larger with a surface temperature of 112,200K. This makes it currently the second smallest known WN star in the galaxy, afterWR 2.
Stars of its kind are characterised by a rapid loss of stellar mass, driven by chemically enriched high-speedstellar winds. It is estimated that it loses mass at the rate of 7x10−5solar masses each year through winds of 1,545 km/s.[6]
The ring nebulaNGC 2359 is excited by theionising radiation of WR7. It is also known as Thor's Helmet or the Duck Nebula. The ring is approximately 4pc across and prominent at wavelengths fromradio toX-ray.[6][7]
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