A little more than 1200 years ago, the Earth has fallen very intense beam of high-energy radiation of unknown origin.
Splash, happened in the years 774-775, found through analysis of the radioactive isotope carbon-14 in tree rings formed during the growing season 775 years in the Northern Hemisphere. Increasing the level of 14C is so obvious that Fusa Miyake and his colleagues at Nagoya University (Japan), concluded: the atmospheric concentration of the isotope increased by 1.2% per year — about 20 times faster than the normal speed of the changes.
14C is formed when high-energy radiation from space falls on the atoms in the upper atmosphere, forming neutrons. They are faced with the nitrogen-14, which then decays to 14C. (By the way, radiocarbon dating and maybe due to the fact that it is always due to background radiation.)
Scientists know only two things that can make a splash 14C: gamma-ray flux from the supernova and the proton storm, which arose because of a solar flare. But both are large enough to have been observed, and other effects. For example, the supernova had to be so bright that it would be visible even during the day, but there have been recorded only in 1006 and 1054, respectively. Besides, the last left no trace in the annals of carbon-14, ie the flash was to be even more powerful.
It is also possible that there was a cataclysm in the distant southern sky, where the astronomers of the time were unable to observe. But if that were to happen, the current X-ray and radio telescopes have found a balance of features extremely bright explosion.
As for the solar flare, the number of "superprotonov" high energy she had to greatly exceed the most intense bursts observed in the history of human letters. In the annals of the stories would have remained on the unprecedented splendor, not to mention the fact that such an outbreak would destroy the ozone layer, with disastrous consequences for the environment.
It should be noted that the research team also found an increase of beryllium-10 in Antarctic ice cores: this is another isotope produced by cosmic rays.
Daniel Baker of the University of Colorado (USA), who was not involved in the study, believes that early to write off the sun. Outbreaks are sometimes associated with coronal mass ejections — huge eruptions of magnetized plasma of the solar atmosphere, which direct the flow of charged particles toward Earth. Possibly accompanied by a coronal mass ejection conditions that cause an unusually large number of protons speeding up to ultrahigh energies, even in the absence of a strong flare.
If so, you should look for in the old books mention of very bright aurora in 774-775 years.
Perhaps the answer to the riddle already know researchers from Queen's University Belfast (UK), who not only found an increase in carbon-14 in tree rings, but found the following testimony of the chronicler Roger Wendover XIII century: "In the year of our Lord 776-e fire and terrible signs were seen in the sky after the sun and the snake appeared in Sussex like from the ground, much to everyone's surprise. " Their work is not yet published.