This has to be one of the most intriguing natural science articles I've seen in a daily paper in a long time:The Earth was hit by a Black Holes generated Gamma ray burst in the days of Charlemagne
"According to a new study, black hole cosmic radiation blasted into the Earth back in the 8th century.
Japanese astrophysicist Fusa Miyake discovered last year clues for the strange event located in the rings of ancient cedar trees that dated back to either 774 or 775 AD.
Researchers teamed together to determine what had caused the surge in carbon-14 in the rings and found no evidence of a supernova, as they had expected. The Anglo-Saxon Chronicle references the appearance of a “red crucifix” seen in the skies after sunset, but that took place in 776 AD, which was too late for when the tree rings show the event took place.
Scientists were also able to rule out a CME burst from the Sun, during which solar flares shoot out cosmic rays, sometimes towards Earth. They wrote in the Monthly Notices of the Royal Astronomical Society, instead, black holes may be the culprit behind the carbon-14 isotope surge in the rings. These isotopes are created when intense radiation hits the atoms in the upper atmosphere, which suggests a blast of energy had once hit Earth.
German-based scientists Valeri Hambaryan and Ralph Neuhauser say two black holes collided and then merged (---) (These two researchers) said the event could only have taken place at least 3,000 light years away from here, otherwise the planet would have been fried."
So pleased we were not closer.
(and by the way, that last line also hints how rare an event it would be. AFAIK, Earth has not been completely grilled any time in the last few hundred million years...)