NGC 2359, Thor’s Helmet

NGC 2359, also known as Thor’s Helmet, is an emission nebula in the costellation Canis Major, located a few degrees northeast of Sirius. Its central star is a Wolf-Rayet star, WR7. The nebula consists of a bubble (akin to NGC 7635, the Bubble Nebula) featuring a complex ionized gas structure that has a shape resembling the helmet of Thor, the god of thunder in Norse mythology. This nebula has also been nicknamed the Duck Nebula.

The main structures of the nebula are green to bluish in color and are particularly prominent in the doubly ionized oxygen band of the spectrum (so-called OIII, peaking at 500.7 nm).

WR7’s distance is not known precisely but is believed to be around 11000 light-years, which means the star is super-massive (>10 solar masses) and very bright (more than 200000 suns).

Below is an image of NGC 2359, taken through a 10-inch GSO RC with an Astro-Physics CCDT67 reducer yielding an equivalent focal ratio of f/5.5. The camera used for imaging is a QHY163M mono camera with an Optolong broad- and narrowband filter set. Total exposure time was 20.5 hours (Ha:OIII:R:G:B 450:450:110:110:110 minutes, 10-minutes subs for narrowband and 5 minutes for broadband).

Enjoy! :-)