Scientist Fusa Miyake suggested that high levels of carbon-14 and beryllium-10 found in tree rings from 775 A.D. could be evidence that Earth was hit by a flash of radiation around that time. The historical record rules out that the radiation could have come from a supernova or solar flare.
There is no human documentation of this happening in the eighth century. But Hambaryan and Neuhauser have explanations for why not: The collision of compact stellar remnants would have released a short burst of radiation, a couple of seconds in duration, without generating visible light. In addition, because life on Earth didn't appear to suffer adverse effects (for example, extinction!), the merging remnants could have been no closer than 3,000 light-years from Earth.
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