Thor's Helmet - January 2012



About the image...

Image Subject – Thor's Helmet Nebula (NGC 2359).
Location Taken – Roque de los Muchachos Observatory (Canary Islands – Spain; 28° 45' 43.4" N, 17° 52' 39.5" W).
Telescope – Isaac Newton Telescope (250cm diameter).
Instrument – Wide Field Camera (WFC).
Focal Ratio – Cassegrein f/3.3.
Exposure – Halpha: 4 x 600s, OIII: 4 x 600s, SII: 4 x 600s.
Image Size – 4096 x 2048 pixels (22 x 11 arcminutes).
Software – PhotoShop CS5.
Images taken and processed by – Rafa Barrena and Daniel López.
Text – Daniel López and Pablo Rodríguez-Gil.

About the object...

Object Type – Wolf-Rayet nebula.
J2000.0 Equatorial Coordinates – 07h 18m 30s; -13º 13’ 48.0’’.
Distance – 15,000 light-years.
Constellation – Canis Major.

NGC 2359, better known as the Thor's Helmet nebula, is actually more like an interstellar bubble, blown as a fast wind from the bright, massive star near the bubble's center sweeps through a surrounding molecular cloud. Known as a Wolf-Rayet star, the central star is an extremely hot giant thought to be in a brief, pre-supernova stage of evolution. It lies about 15,000 light years from Earth in the constellation Canis Major, measuring about 30 light years.

It is one of the best known Wolf-Rayet nebular structures, along with NGC 6888 (which appeared as AIM in September 2006). It's known as Thor's Helmet due to its remarkable resemblance to depictions of the headwear donned by the famed Norse god of thunder. This INT image captures striking details of the nebula's filamentary structures. The bluish colour remarks the strong emission due to oxygen atoms in the glowing gas. In fact, it can be visually seen with telescopes of moderate aperture using an [OIII] narrow-band filter.