Thor’s Helmet is a wind-blown nebula surrounding the Wolf–Rayet star WR 7. The star has shed material throughout its evolution, and its current high-speed wind is plowing into surrounding gas, producing an expanding bubble, shock fronts, and the curved filaments visible in deep images.

The bright central shell is only part of the structure. Fainter arcs and extensions trace the complicated interaction between the stellar wind and an uneven interstellar environment, giving NGC 2359 the distinctive “helmet and wings” appearance behind its nickname.

At the center of the nebula is WR 7, a Wolf–Rayet star in a brief, violent late stage of massive-star evolution. Its wind travels at enormous speed and plows into slower material shed earlier in the star’s life, producing the bright shock fronts and oxygen-rich arcs that define the helmet-like shell.

The nickname Thor’s Helmet is a modern reference to Thor, the thunder god of Norse mythology, inspired by the nebula’s broad central dome and wing-like extensions. It is not an ancient name for this patch of sky—the nebula is far too faint to see with the unaided eye.

Its constellation, Canis Major, belongs to a different mythic tradition. In Greek sky lore the Great Dog is commonly associated with Orion and is led by Sirius, the brightest star in the night sky.

Thor’s identity runs much deeper than the modern helmet nickname. In Norse tradition he is the thunder god, a defender of gods and humans whose hammer Mjölnir returns to his hand after being thrown. The association with thunder, strength, and a distinctive helmeted warrior image made the nebula’s shape an especially natural target for a modern mythological nickname.