There are many nebulae in our galaxy, ranging from supernova remnants to planetary nebulae. They come in many shapes, sizes and colors, each with their own distinct qualities. Thor's helmet may not be the largest, brightest or most beautiful among them (the last thing is entirely subjective), but it is certainly unlike most nebulae.
Otherwise known as NGC 2359, Thor’s Helmet Nebula can be found approximately 15,000 light-years from Earth toward the Canis Major constellation.
Instead of rising from the ash of a supernova like a stellar phoenix, no star had to die (at least not yet) for Thor's Helmet Nebula—named as such due to its resemblance to the helmet of Thor from Norse mythology—to be born. Instead, it is the intricate workings of a volatile high-mass star—a Wolf-Rayet star known as HD 56925.
Overall, the star continues to weave a truly large web, spanning around 30 light-years across. It will until there is nothing left, which will happen sooner rather than later. You see, stars like this start dying the minute they are born, ejecting vast quantities of their material into space.. lost forever. With HD 56925, around 1 solar mass of material is shed every 100,000 years.
Taken by Adam Block, this image landed him a spot in the astronomy photographer of the year contest. See more of this work below (a larger copy of this one can be found here):