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Named Miyake events after the lead author of the first study to describe them, the spikes occur roughly once every 1,000 years or so and are recorded as sudden increases in the radiocarbon levels of ancient tree rings. The leading theory among scientists is that Miyake events are solar flares that are 80 times more powerful than the strongest flare ever recorded. But a new study...suggests that the origin of the radiation bursts could be even more mysterious than first thought. Scientists have spotted six Miyake events in tree rings so far, indicated by sudden, single-year leaps in the concentrations...

NASA, ESA, J. Hester, A. Loll (ASU) ===================================================================== Supernovas may have affected the Earth’s climate in the last 40,000 years. Tree-ring data suggests supernovas caused spikes in radiocarbon. Could the next nearby supernova cause a collapse of civilization? ====================================================================== Dendrochronology is a fancy word for tree-ring dating, where the age of a tree can be determined by the number of growth rings across its trunk. But there’s a lot more to learn from looking at a tree’s rings than simply its age. Like fingerprints, tree rings give scientists clues to what the world was like when a tree was alive....

Phil PlaitNovember 16, 2015 A new study says that violent space weather that could cost $2 trillion in damage is more common than previously thought In the years 774 and 993, the Earth was attacked from space. Not by aliens, but by a natural event—and it was very, very powerful. Whatever it was, it subtly altered the chemistry of our planet’s atmosphere, creating trace amounts of radioactive elements like chlorine-36, beryllium-10, and carbon-14. And those provide the clue to what the event was: Those isotopes are created when high-energy protons slam into our air. That means the source must have...

According to an Old English manuscript chronicling the history of the Anglo-Saxons, a mysterious "red crucifix" appeared in the "heavens" over Britain one evening in A.D. 774. Now astronomers say it may have been the supernova explosion that sprinkled unexplained traces of carbon-14 in tree rings that year, halfway around the world in Japan. Jonathon Allen, an undergraduate student at the University of California, Santa Cruz, made the connection this week after listening to a Nature podcast. He heard a team of Japanese scientists discussing new research in which they measured an odd spike in carbon-14 levels in tree rings...

From the AGU weekly highlights: Large solar proton event explains 774-775 CE carbon-14 increase Tree ring records indicate that in 774-775 CE, atmospheric carbon-14 levels increased substantially. Researchers suggest that a solar proton event may have been the cause. In solar proton events, large numbers of high-energy protons are emitted from the Sun, along with other particles. If these particles reach EarthÂ’s atmosphere, they ionize the atmosphere and induce nuclear reactions that produce higher levels of carbon-14; the particles also cause chemical reactions that result in depletion of ozone in the ozone layer, allowing harmful ultraviolet radiation to reach the...

(Phys.org)—Until recently, the years 774 and 775 were best known for Charlemagne's victory over the Lombards. But earlier this year, a team of scientists in Japan discovered a baffling spike in carbon-14 deposits within the rings of cedar trees that matched those same years. Because cosmic rays are tied to carbon-14 concentrations, scientists around the world have wondered about the cause: a nearby supernova, a gamma ray burst in the Milky Way or an intense superflare emanating from the Sun? Now, Adrian Melott, professor of physics and astronomy at the University of Kansas and Brian Thomas, KU alumnus and professor...

Just over 1,200 years ago, the planet was hit by an extremely intense burst of high-energy radiation of unknown cause, scientists studying tree-ring data have found. The radiation burst, which seems to have hit between AD 774 and AD 775, was detected by looking at the amounts of the radioactive isotope carbon-14 in tree rings that formed during the AD 775 growing season in the Northern Hemisphere. The increase in 14C levels is so clear that the scientists, led by Fusa Miyake, a cosmic-ray physicist from Nagoya University in Japan, conclude that the atmospheric level of 14C must have jumped...