A nearby short gamma-ray burst could have produced an intense blast of radiation that hit Earth around A.D. 775, according to new German-led research.
Excess amounts of carbon-14 and beryllium-10 isotopes in tree rings formed at that time mean Earth was probably struck by a blast of radiation, although there are no historical records of a supernova explosion, or any supernova remnants that can be observed now.
Instead, a merger between two compact stellar remnants could have generated an intense yet invisible burst of gamma rays, perhaps lasting less than two seconds.
The colliding objects could have been black holes, neutron stars, or white dwarf stars, and would have had to be at least 3,000 light-years away as there is no record of any extinctions on Earth at that time.
“If the gamma-ray burst had been much closer to the Earth it would have caused significant harm to the biosphere,” said research leader Ralph Neuhauser at the Astrophysics Institute of the University of Jena in a press release.
“But even thousands of light-years away, a similar event today could cause havoc with the sensitive electronic systems that advanced societies have come to depend on.”
Some visible light may have been emitted, but might only have lasted a few days and therefore have been easily missed.
However, any resultant merged object could be detectable now, such as a 1,200-year-old black hole.
“The challenge now is to establish how rare such carbon-14 spikes are, i.e., how often such radiation bursts hit the Earth,” Jena concluded.
“In the last 3,000 years, the maximum age of trees alive today, only one such event appears to have taken place.”
The findings were published in the Monthly Notices of the Royal Astronomical Society.
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