Thor’s Helmet (NGC 2359)
NGC 2359 is an emmission/reflection nebula excited by the powerfull wind of the 11.4 mag Wolf-Rayet Star HD 56925 (WR7) at a distance of about 1600 lightyears. At this distance, the true diameter of the filamentary bubble measures about 230x120 lightyears.
This image is composed of long exposed narrowband (Ha/OII) plus strong color (RGB) data and was choosen as APOD.
[description from O’Meara]