More than 1,200 years ago, intense bursts of charged particles slammed into Earth.
Yet, the only remaining evidence of the extreme cosmic event — which scientists say should have been visible in the sky — is hidden in the rings of two Japanese cedar trees.
According to Jessica Griggs of New Scientist, Fusa Miyake from Nagoya University in Japan found higher-than-normal levels of carbon-14 in tree rings that formed between 774 and 755AD.
Carbon-14 is produced when high-energy radiation, typically from a supernova explosion or giant solar flare, reacts with nitrogen and oxygen in the Earth’s atmosphere.
Miyake tells Richard A. Levett of Nature magazine, however, that neither a massive supernova or solar flare are likely to have caused spikes in carbon-14 “because each should have been large enough to have had other effects that would have been observed at the time.”
The problem is there are no historical records of a powerful aurora (produced by a solar flare) from around the same time increased levels of carbon-14 were found in the tree rings.
On top of that, if a solar flare was the source, it would have to be the largest outburst ever recorded and probably would have destroyed the ozone layer, Levett writes.
The only thing scientists do know?
“Some very energetic event occurred in about ad 775,” scientist Daniel Baker told Nature.
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