NGC2359 Thor's Helmet

NGC 2359 is an emission nebula in the constellation Canis Major located just over 8 degrees from Sirius (α Canis Majoris). Its unusual shape, similar to the helmet of a Viking warrior, has led to it being also known as the Thor’s Helmet Nebula.

It can be observed, in dark skies, with small telescopes at 47x with the help of filters of the Oxygen type.

Technical data:

Telescope: S/C 8″
Focal Length Reducer: Meade 6.3
Filters: Ha 12nm/O[III] 12nm/S[II] 12nm
Telescope Guide: SkyWatcher ED80
Mount: LX200 GPSR
Guide CCD: QHY5
CCD Temp:-5º
Ambient Temp:0º
Location: Anunaki Observatory / Rivas Vaciamadrid (Madrid)

The star inside the bubble, called WR 7 (HD 56925), has an apparent magnitude of 11.5. It is a Wolf-Rayet star and is the source that illuminates this Wolf-Rayet nebula. Nebulosity is the result of the interaction between the stellar wind coming from the hot star and interstellar matter. The wind compresses the interstellar matter producing a bubble of gas around the star. The mass of the bubble is estimated at about 20 solar masses.

VLA image of NGC 2359 continuous radio emission at 1465 MHz

Although similar in nature to the Bubble Nebula (NGC 7635), interaction with a neighboring molecular cloud appears to have contributed to shaping the nebula’s complex shape.