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Mysterious radiation burst recorded in tree rings

ananyo (2519492) writes | more than 2 years ago

Earth 0

ananyo (2519492) writes "Just over 1,200 years ago, the planet was hit by an extremely intense burst of high-energy radiation of unknown cause, scientists studying tree-ring data have found.
The radiation burst, which seems to have hit between ad 774 and ad 775, was detected by looking at the amounts of the radioactive isotope carbon-14 in tree rings that formed during the ad 775 growing season in the Northern Hemisphere. The increase in 14C levels is so clear that the scientists conclude that the atmospheric level of 14C must have jumped by 1.2% over the course of no longer than a year, about 20 times more than the normal rate of variation (abstract abstract).
Yet, as the only known events that can produce a 14C spike are supernova explosions or giant solar flares, and neither event was observed at the time, astronomers have a cosmic mystery on their hands."

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