NGC 2359: Thor's Helmet Nebula

Thor's Helmet Nebula (NGC 2359) is a gorgeous emission nebula in the constellation Canis Major.
At the core of the nebula, lies a supermassive star (HD 56925, mag +10,4) that illuminates the nebulosity via hydrogen ionization.
NGC 2359 is about 12000 l.y. away from us and extends 30 l.y. across.