NGC 2359 is an emission nebula in the
constellation Canis Major. The nebula is approximately 15,000
light-years away and 30 light-years in diameter. The central
star is the Wolf-Rayet star HD 56925, an extremely hot giant
thought to be in a brief, pre-supernova stage of evolution.
Interactions with a nearby large molecular cloud are thought to
have contributed to the more complex shape and curved bow-shock
structure of Thor's Helmet. Visually
through most amateur telescopes, this nebula is very faint, and
requires Narrow-Band (UHC or O-III) filters to enhance contrast.