Magnitude 11.4 Apparent magnitude (V) 11.4 | ||
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Similar NGC 2359, Tau Canis Majoris, Gamma Canis Majoris, Zeta Canis Majoris | ||
WR 7 (HD 56925) is a Wolf-Rayet star in the constellation of Canis Major. It lies at the centre of a complex bubble of gas which is shocked and partially ionised by the star's radiation and winds.
The distance is uncertain, with estimates between 3.5 kiloparsecs (11,410 lightyears) 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 280,000 times brighter than our Sun, 16 times more massive, and 1.41 times larger with a surface temperature of 112,000 Kelvin.
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.
The ring nebula NGC 2359 is excited by the ionising 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 from radio to x-ray.