| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 18m 29.1316s |
| Declination | -13° 13′ 01.507″ |
| Apparent magnitude (V) | 11.4 |
| Characteristics | |
| Spectral type | WN4 |
| Variable type | None |
| Astrometry | |
| Proper motion (μ) | RA: -2.99 mas/yr Dec.: 3.46 mas/yr |
| Parallax (π) | -1.84 ± 2.73 mas |
| Distance | 3662 ly (1124 pc) |
| Other designations | |
In astronomy WR 7 or HD 56925/HIP 35 378 is a Wolf-Rayet star which is a central part of the nebula NGC 2359 (also known as the Thor's Helmet Nebula) in the constellation of Canis Major.
The distance is uncertain, varying between 3.5 kiloparsecs (11,410 lightyears) and 6.9 kiloparsecs (22,500 light years). Stars of its kind are characterised by a rapid loss of stellar mass, driven by chemically enriched high-speed stellar winds. It is estimated that it loses mass at the rate of 7x10−5 solar masses each year through winds of 1,545 km/s.
Studies of the interaction between WR 7 and the surrounding nebula assumes a distance of 5 kiloparsecs, and have discovered the existence of a HI region of 70x37 kiloparsecs that expands at 12 km/s, possibly created by the progenitor of the current star, a type-O main sequence star. It seems likely that there is a bow shock acting on the southern edge of the nebula, possibly reduced when the star was at the stage of red supergiant.
References [edit]
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