About 700 years ago, light from a tremendous explosion reached Earth that should have appeared almost as bright as a full Moon. The bright spot should have lasted for weeks, yet no notation of such an occurrence has been found in historical records. They deduced that an explosion much younger and closer than the supernova that caused Vela must have occurred, and even computed explosion characteristics from the amounts of radioactive elements present. Perhaps people were too busy, surviving records are too incomplete, or the explosion was somehow too dim. Astronomers and historians continue to contemplate the clues.
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