AAPOD²: 4 June 2016

Thor's Helmet is an emission nebula in the constellation of Canis Major nearly 12,000 light years away. The central star is a massive and unstable Wolf-Rayet star WR7, an extremely hot giant. Very strong winds from this star interact with the surrounding stellar medium at very high speed (millions of kilometers per hour) causing it to glow blue-green colour and create shock wave arcs seen in the central bubble-like structure.