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Thor's Helmet
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Intense X-rays sculpt Thor's neon-hued helmet

Intense_X-rays_sculpt_Thor_s_neon-hued_helmet_node_full_image_2.jpg

This brightly coloured scene shows a giant cloud of glowing gas and dust known as NGC 2359. This is also dubbed the Thors Helmet nebula, due to the arching arms of gas stemming from the central bulge and curving towards the top left and right of the frame, creating a shape reminiscent of the Norse gods winged helmet.
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NGC 2359
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NGC 2359 (also known as Thor's Helmet, Sh2-298 and Gum 4) is an emission nebula in the constellation Canis Major. The nebula is approximately 15,000 light-years away and 30 light-years in size. The central star is a Wolf-Rayet star, listed as WR 7, HD 56925 and HIP 35378, with a magnitude equal to +10.4, it is an extremely hot giant, thought to be in a brief pre-supernova stage of evolution. It is similar in nature to the Bubble Nebula; interactions with a nearby large molecular cloud are thought to have contributed to the more complex shape and curved bow-shock structure of Thor's Helmet.

It is also listed in the Sharpless catalogue as Sh2-298 and Gum catalogue 4.

NGC 2359 was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Datchet, Berkshire, on the 31st January 1785.

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Title: On the diffuse X-ray emission from the Wolf-Rayet Bubble NGC 2359
Author: J.A. Toalį, M.A. Guerrero, Y.-H. Chu, R.A. Gruendl

A recent XMM-Newton observation (Zhekov 2014) has revealed diffuse X-ray emission inside the nebula NGC 2359 around the Wolf-Rayet star WR 7. Taking advantage of an improved point-source rejection and background subtraction, and a detailed comparison of optical and X-ray morphology, we have reanalyzed these X-ray observations. Our analysis reveals diffuse X-ray emission from a blowout and the presence of emission at energies from 1.0 to 2.0 keV. The X-ray emission from NGC 2359 can be described by an optically-thin plasma emission model, but contrary to previous analysis, we find that the chemical abundances of this plasma are similar to those of the optical nebula, with no magnesium enhancement, and that two components at temperatures T_1=2x10^6 K and T_2=5.7x10^7 K are required. The estimated X-ray luminosity in the 0.3 - 2.0 keV energy range is L_X=2x10^33 erg s^-1. The averaged rms electron density of the X-ray-emitting gas (n_e \lesssim 0.6 cm^-3) reinforces the idea of mixing of material from the outer nebula into the hot bubble.

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Google earth file: NGC 2359.kmz (2kb, kmz)



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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. The central star is an extremely hot giant Wolf-Rayet star, 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.
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