This target has been high on my list for a while -- Thor's Helmet! Such an incredible nebula, with a "super" name
Also known as the Duck Nebula, or by its catalog number NGC 2359, Thor's Helmet is an emission nebula up in the constellation Canis Major, which is east of the constellation Orion and in the plane of the wintertime Milky Way. The nebula is enormous -- 30 lightyears across, and still fairly large on the sky despite its almost 12,000 lightyear distance! The central star that is energizing and shaping this monstrosity is Wolf-Rayet star WR7, an extreme star that is 280,000 times brighter than the Sun, 16 times more massive, and has a surface temperature of 112,000 K (compared to the Sun's 5,700 K)! The gas ejected by this star is interacting with a nearby cloud of molecular dust, which is partly responsible for the nebula's shape, and the nebula is expanding at a rate of 10-30 km/s (22,000 - 67,000 mph)!
This image is composed of two narrowband emission channels -- hydrogen-alpha (set as red) and oxygen-III (set as green and blue). Hydrogen and oxygen gas ejected and then energized by the central star emit light at particular wavelengths -- a deep red for hydrogen, and a blue-green color for oxygen, so the colors here are approximately correct. (Except for the background stars). I thought about adding the color data I also took to get accurately-colored stars, but the data were kind of a mess and I decided I didn't feel like dealing with them when the narrowband data was so good
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