15 000 light-years
Thor's Helmet is a rare example of a Wolf-Rayet star. Around 40 times the mass of our Sun, this type of star is young and extremely bright. It generates a wind that blasts outwards from the star at millions of kilometres per hour. Because Wolf-Rayet stars burn so brightly and shed so much material, scientists think they represent a brief stage before the star explodes as a supernova.
Credit: Canada-France-Hawaii Telescope / Coelum / J.C. Cuillandre & G. Anselmi.
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