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Post Info TOPIC: 775 AD Event
Blobrana


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774-775 carbon-14 spike
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The 774-775 carbon-14 spike was an increase of 1.2% in the carbon-14 content of tree rings during the years AD 774 or 775, which was about 20 times higher than the normal rate of variation. It was found during a study of Japanese cedar trees, with the year of occurrence determined through dendrochronology.
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Blobrana


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RE: 775 AD Event
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Title: Comet Encounters and Carbon 14
Authors: David Eichler, David Mordecai

The ^{14}C production of shock-accelerated particles is calculated in terms of the total energy released in energetic particles. The recently reported 1.2% jump in the ^{14}C content of the atmosphere in the year C.E. 775, it is found, would require \gtrsim 10^{34} erg in energetic particles, less than first estimates but far more than any known solar flare on record. It is noted that the superflare from a large comet (comparable to C/Hale-Bopp) colliding with the sun could produce shock-accelerated GeV cosmic rays in the solar corona and/or solar wind, and possibly account for the CE 775 event. Several additional predictions of cometary encounters with the sun and other stars may be observable in the future.

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Blobrana


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Posts: 131433
Date:
774 AD
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Ancient text gives clue to mysterious radiation spike

An eerie "red crucifix" seen in Britain's evening sky in ad 774 may be a previously unrecognised supernova explosion - and could explain a mysterious spike in carbon-14 levels in that year's growth rings in Japanese cedar trees. The link is suggested today in a Nature Correspondence by a US undergraduate student with a broad interdisciplinary background and a curious mind.
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Blobrana


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Date:
RE: 775 AD Event
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 Mysterious radiation burst recorded in tree rings

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 by 1.2% over the course of no longer than a year, about 20 times more than the normal rate of variation. Their study is published online in Nature today
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Blobrana


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Posts: 131433
Date:
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Vast cosmic event leaves record in ancient trees

The wooden hearts of two cedar trees hold a 1200-year-old cosmic mystery - evidence of an unexplained event that rocked our planet in the 8th century.
Cosmic rays are subatomic particles that tear through space. When they reach Earth they react with the oxygen and nitrogen in the atmosphere, producing new particles. One of these - carbon-14 - is taken up by trees during photosynthesis and is "fixed" in the tree's annual growth ring.
Fusa Miyake at Nagoya University, Japan, and his colleagues examined the carbon-14 content of two Japanese cedar trees and were surprised to find that there was a 1.2 per cent increase in the amount of the isotope between AD 774 and 775. The typical annual variation is just 0.05 per cent.
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