A Wolf-Rayet star in NGC 2359
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A Wolf-Rayet star in NGC 2359, HD 56925, ngc2359.jpg
Top left is NE. Image width is about 24 arc min
Image and text © 1979-2010, Australian Astronomical Observatory, photograph by David Malin.

NGC 2359 (sometimes known as Thor's Helmet) is the nebula produced by a single, extremely hot star HD 56925 in Canis Major. This is one of the rare Wolf-Rayet stars, whose intrinsic brilliance is combined with high rates of mass loss from its surface. This material is ejected from the star with velocities which approach 2000 kilometers per second, and this violent outflow quickly reduces the mass of the star which in turn reduces the instability. The rapidly-moving ejected material interacts with the gas and dust around the star producing the cosmic bubble seen here. Such stars are unusual, largely because extreme behaviour of this kind cannot be sustained for long. This particular example is spectacular because it happens to inhabit a part of our Galaxy rich in interstellar gas, rather like the the Bubble nebula, NGC 7636.

Related Images
INT 10.   The Bubble nebula, NGC 7635
Constellation of Canis Major (external site)

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Updated by David Malin, 2010, August 1