(FILE PHOTO) In this image released by the NASA, the Chandra X-ray Observatory and the Hubble Space Telescope shows a halo of hot gas surrounding spiral galaxy NGC 4631 that is similar to the Milky Way galaxy while in space. (Photo by NASA/Getty)
Astronomers call it the monster. It was the biggest and brightest cosmic explosion ever witnessed. Had it been closer, Earth would have been toast.
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