Abstract
A large and sudden increase in radiocarbon (14C) around AD 773 are documented in coral skeletons from the South China Sea. The 14C increased by ~ 15‰ during winter, and remain elevated for more than 4 months, then increased and dropped down within two months, forming a spike of 45‰ high in late spring, followed by two smaller spikes. The 14C anomalies coincide with an historic comet collision with the Earth's atmosphere on 17 January AD 773. Comas are known to have percent-levels of nitrogen by weight, and are exposed to cosmic radiation in space. Hence they may be expected to contain highly elevated 14C/12C ratios, as compared to the Earth's atmosphere. The significant input of 14C by comets may have contributed to the fluctuation of 14C in the atmosphere throughout the Earth's history, which should be considered carefully to better constrain the cosmic ray fluctuation.
Highlights
A large and sudden increase in radiocarbon (14C) around AD 773 are documented in coral skeletons from the South China Sea
Their modeling showed that the atmospheric level of 14C must have jumped over the course of no longer than a year, corresponding to an increase 10 times larger than the average production from Galactic cosmic rays and 20 times larger than that expected over 2 3 11 yr solar cycles
Given that no detectable increase in 14C corresponding to supernovas SN 1006 and SN 1054 were observed[7,8], it is argued that much higher energies would be required for the M12 event, if it is related to a supernova[7]
Summary
A large and sudden increase in radiocarbon (14C) around AD 773 are documented in coral skeletons from the South China Sea. Given that no detectable increase in 14C corresponding to supernovas SN 1006 and SN 1054 were observed[7,8], it is argued that much higher energies would be required for the M12 event, if it is related to a supernova[7] Alternative explanations for this mysterious 14C elevation include a highly energetic radiation burst, e.g., proton storms from giant solar flares[9,10], a giant cometary impact upon the Sun[11], or floods of c-rays from supernova explosions[12]. We analysed 14C contents for half-annual-resolution subsamples at depths of 1.04–42.65 cm and ,2-year biweekly-resolution subsamples at depths of 12.25–17.19 cm (Fig. 1, Table S2 and S3)
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