Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. Image colours therefore represent the relative million degree temperatures of the x-ray emitting regions, red being the coolest and blue the hottest. Remains of the star that exploded as Supernova 1987a appear here as the white x-ray source at the lower right, while another supernova remnant , cataloged as N157D is the brightest source at the upper left.
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