The European Space Agency (ESA) just released a brightly colored image of NGC 2359. The nebula is also known as Thor's Helmet, due to the gas arches stemming out of the central bulge and curving towards the top — which create a shape reminiscent of the Norse god's winged helmet.
The stunning image is actually a combination of two photos — captured by the ESA XMM-Newton space observatory's EPIC cameras and the Cerro Tololo Inter-American Observatory's Stars and Shadows Remote Observatory South.
The vivid colors provide the legend to understanding the nebula's composition. The bright blue patches reveal X-ray emissions spotted by the EPIC cameras, while the pale green and red regions glowing from ionized hydrogen and oxygen are shown by the Stars and Shadows.
The intense X-ray emissions documented by the XMM-Newton are coming from a Wolf-Rayet star in the middle of the nebula called HD 56925. Old and enormous, the star is releasing great amounts of material at a dizzying rate, losing mass equivalent to the Sun in under 100,000 years. Mass loss appears as wind moving around the nebula at speeds of 932 miles per second.
With such violent inhabitants within, Thor's Helmet has taken on a messy shape. The central bubble is enveloped by gaseous filaments, thick dark-dust channels and bright bursts — where stellar material swept away by winds collides with surrounding gas to trigger shock waves that ripple across the region.
The blue patches in Thor's Helmet highlight the hottest regions in the nebula: a blowout on the lower left and its central bubble. Gas within the NGC 2359 is believed to reach a temperature range between several million and tens of millions of degrees.
The XMM-Newton has been orbiting the Earth since 1999, but the space observatory's contribution to the image of Thor's Helmet was captured in 2013. The image was first released in the image gallery of the XMM-Newton.
NGC 2359 is located some 15,000 light-years away from Earth and measures around 30 light years wide. Investigators who brought together the images of Thor's Helmet include M.A. Guerrero and J.A. Toala from IAA-CSIC, R.A. Gruendil from UIUC and Y.-H. Chu from UIUC/ASIAA.
Astronomical database entries offering more information about the nebula can be found at the NASA/IPAC Extragalactic Database and the Set of Identifications, Measurements and Bibliography for Astronomical Data or SIMBAD.