Thor's Helmet

Deep in the constellation Canis Major lies one of the most spectacular nebulae in the southern sky: Thor's Helmet. Catalogued as NGC 2359, this cosmic bubble spans approximately 30 light-years and sits around 15,000 light-years from our solar system.

At its heart burns WR 7 (HD 56925), an extremely massive and hot Wolf-Rayet star whose violent stellar winds have literally carved this bubble into the surrounding interstellar medium. NGC 2359 holds the distinction of being the first Wolf-Rayet nebula ever discovered, first identified by William Herschel in 1785. The central star is nearing the end of its life and is expected to explode as a supernova within the next few thousand years.

The complex shape of the Helmet — with its characteristic filaments and bow-shock structure — results from the interaction between WR 7's winds and a large nearby molecular cloud. The nebula contains several hundred solar masses of ionised material.

This image was captured using an IDAS NBZ-II filter that isolates hydrogen and ionised oxygen emissions, revealing the faintest gaseous structures of the nebula.