A cosmic catastrophe may have occurred in our part of the galaxy less than 1300 years ago. A similar event today could have damaging effects on our technological civilization.
A new paper by astronomers Valeri Hambaryan and Ralph Neuhӓuser at the University of Jena, Germany suggests that a short-duration gamma-ray burst from the merging of two stellar remnants may have caused an intense blast of high-energy radiation that hit the Earth in the 8th century. The paper, A Galactic short gamma-ray burst as cause for the 14C peak in AD 774/5, is published in the Monthly Notices of the Royal Astronomical Society.
Hambaryan and Ralph Neuhӓuser seek to explain a discovery by cosmic-ray physicist Fusa Miyake of Nagoya University, Japan in 2012. Professor Miyake detected high levels of Carbon-14 and Beryllium-10 in tree rings formed in 775. This finding suggests that a burst of radiation struck the Earth in the year 774 or 775.
A gamma-ray burst could have come from a nearby supernova explosion, but no supernova was recorded in observations from those years and no remnant has been found. Solar flares are another possible culprit, but flares are not powerful enough to cause the level of C-14 that has been detected. Nor do historical records indicate displays of auroral activity that would indicate a large flare had taken place.
Dr. Hambaryan and Dr. Neuhӓuser suggest that the radiation burst may have resulted from the collision and merger of two compact stellar remnants (black holes, neutron stars, or white dwarfs.) In these mergers, the burst of gamma rays is intense but short, typically lasting less than two seconds, accompanied by little visible light.
Based on the C-14 measurements, Hambaryan and Neuhӓuser believe the gamma-ray burst originated between 3,000 and 12,000 light years from Earth. If the merging stars had been closer than 3,000 light years, the gamma-ray intensity would have led to the extinction of some terrestrial life.
Dr. Neuhӓuser said, “If the gamma-ray burst had been much closer to the Earth, it would have caused significant harm to the biosphere. 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. The challenge now is to establish how rare such Carbon-14 spikes are; how often such radiation bursts hit the Earth. In the last 3000 years, the maximum age of trees alive today, only one such event appears to have taken place.”