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 year A.D. 774 or 775. They thought the spike must have come from a burst of high-energy radiation striking the upper atmosphere and triggering an increase in the rate of carbon-14 formation.
(Carbon-14, a radioactive version of a carbon atom with six protons and eight neutrons, forms when gamma rays from space strip atmospheric atoms of their neutrons, which then collide with the isotope nitrogen-14 and cause it to radioactively decay into carbon-14.)
But a mystery was afoot: the scientists could not find any records indicating a massive supernova (stellar explosion) or solar flare was observed in the skies in the A.D. 770s, and the event would have had to be visible to produce a sufficiently large influx of radiation.
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Article by Life’s Little Mysteries Staff