Helmet Nebula by Supershell

Helmet Nebula is an emission nebula in the constellation Canis Major. The nebula is approximately 11.96 thousand light years away and 30 light years in size. The central star is the Wolf-Rayet star WR7, an extremely hot star thought to be in a brief pre-supernova stage of evolution.

The nebula has an overall bubble shape, but with complex filamentary structures. The nebula contains several hundred solar masses of ionised material, plus several thousand more of unionised gas. It is largely interstellar material swept up by winds from the central star, although some material does appear to be enriched with the products of fusion and is likely to come directly from the star. The expansion rate of different portions of the nebula varies from 10 km/s to at least 30 km/s, leading to age estimates of 78,500 - 236,000 years.

Shell #1 - journey
Shell #2 - space