Cassiopeia A is the youngest supernova remnant in our Milky Way Galaxy, believed to be the leftovers of a massive star that exploded over 300 years ago. The material ejected during the supernova smashed into the surrounding gas and dust at about 16 million kilometres per hour. This collision superheated the debris field to millions of degrees, causing it to glow brightly in X-rays as seen here by the Chandra X-ray Observatory.
Credit: Chandra, NASA / CXC / MIT / UMass Amherst / M.D.Stage et al.
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