NGC 2359 / THOR'S HELMET

NGC 2359 (also known as Thor's Helmet Nebula and Gum 4) is an emission nebula located in the constellation Canis Major.

Finding its exact position in the sky is not at all simple; the only less difficult way is to follow the alignment between the stars ι and γ Canis Majoris and then, continuing approximately twice their distance, deviate the direction by approximately 10° towards the east. Outside the reach of any binoculars, it is instead visible through telescopes with apertures of at least 120mm in diameter, in which it appears as a speck in the shape of the letter Q. In photography, however, it appears to be a marvelous object. At the center of the nebula there is a very hot Wolf-Rayet star, which illuminates it, exciting its hydrogen and ionizing it; this star is cataloged as WR 7, or HD 56925, and has a magnitude of 10.40, and would be mainly responsible for the formation of the nebula, composed of the gas expelled by the star itself.

Other hypotheses to explain the arc-shaped jets observed in the cloud include that the central star about 7 million years ago was a red supergiant, whose eastward motion caused a shock wave when the stars collided. the strong stellar wind and the surrounding interstellar medium, very dense due to the presence of a molecular cloud, causing the visible structure; Still other hypotheses mention other stars as being responsible for the arcuate structure of the nebula.