Astronomers using the EPIC cameras on ESA’s XMM-Newton space observatory and the Star Shadows Remote Observatory at New Mexico Skies and Cerro Tololo Inter-American Observatory have snapped an amazing view of a massive cloud of gas and dust known as Thor’s Helmet Nebula.
This composite image shows the Thor’s Helmet Nebula, also known NGC 2359. It combines X-ray data collected by XMM-Newton (blue) with optical observations from the Star Shadows Remote Observatory (green and red). North is to the left, west is up. Image credit: J.A. Toala & M.A. Guerrero, IAA-CSIC / Y.-H. Chu, UIUC-ASIAA / R.A. Gruendl, UIUC / S. Mazlin, J. Harvey, D. Verschatse & R. Gilbert, SSRO-South / ESA.
Thor’s Helmet Nebula, also catalogued as Gum 4, Sharpless 2-298 or NGC 2359, is an emission nebula located in the constellation of Canis Major, about 11,960 light-years away from Earth.
It is approximately 30 light-years in size and has a very complex structure – it consists of a main shell with a series of blisters, blowouts, and very prominent and long filaments.
The nebula is blown by the powerful stellar wind of HD 56925, an evolved massive star.
This unusual star, also known as the Wolf-Rayet star WR7, is classified as being a Wolf-Rayet type and is very rare. Wolf-Rayet stars are incredibly hot and expel their outer layers of gas at tremendous velocities.
The strong shock of the HD 56925’s stellar wind with the circumstellar material produces hot plasma at temperatures above 2 million degrees.
The distribution of the hot gas inside the Thor’s Helmet Nebula has been mapped by the XMM-Newton EPIC instrument.
The blue patches highlight the nebula’s hottest regions: the central bubble and a blowout to its lower left.
The red and green regions trace the glow from ionized hydrogen and oxygen, as seen by the Star Shadows Remote Observatory.
The results will be published in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).
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J.A. Toalá et al. 2015. On the diffuse X-ray emission from the Wolf-Rayet Bubble NGC 2359. MNRAS, in press; arXiv: 1410.2037
