(ORDO NEWS) — Tree rings have preserved traces of sharp peaks in the content of radioactive carbon in the earth’s atmosphere. They are usually associated with anomalously powerful solar flares.
However, a new analysis showed that everything is not so simple and our luminary is hardly associated with these events. Perhaps it’s all about nearby supernova explosions.
Carbon dioxide in the earth’s atmosphere always contains small amounts of radioactive carbon-14. From here, it enters living organisms, which contain it in the same concentration as in the air.
Certain events can change the amount of carbon-14 in the atmosphere, and these changes remain recorded in the annual rings of wood, allowing the remains of long-dead trunks to be used as a tool for dating natural phenomena and archaeological finds.
For example, Miyake events help to tie a tree cut to a specific date – short-term and strong jumps in the atmospheric concentration of carbon-14.
The most powerful of them dates back to 774 , although there are up to six such events in total, also related to 993 and 660 AD, as well as 5259, 5410 and 7176 BC. During these years, plants all over the planet accumulated several times more radioactive carbon than usual.
The exact reason for these jumps remains unknown. Some scientists associate them with explosions of relatively nearby supernovae or with gamma-ray bursts.
And the most popular hypothesis considers the Miyake events to be the result of abnormally high solar activity and the occurrence of powerful flares. In particular, they are indicated by the chronicles of 774, in which unusually strong auroras are recorded.
However, the new work of scientists from the Australian University of Queensland refutes the connection of the Miyake events with the Sun.
The authors of the study approached the problem systematically, proceeding from the fact that the correct interpretation of annual tree rings requires an accurate understanding of the global carbon cycle, which directly affects the accumulation of radioactive isotopes.
Scientists relied on the block model of this cycle. It considers the movement of carbon between several “reservoirs”: the atmosphere, the biosphere, and so on.
Pope and colleagues have developed a computer program that calculates the carbon cycle in terms of a block model, and have carried out such calculations for the last ten thousand years.
They gave a more detailed picture of the Miyake events and showed that they do not match the data on the cyclic activity of the Sun.
Moreover, the carbon accumulation profile turned out to be different for trees in different regions of the planet. In the same year 774, some of them retained a sharp peak of carbon-14, while others were smoother, extended over several years.
Scientists find it difficult to offer another explanation for the events of Miyake, alternative to the hypothesis of solar activity.
On the one hand, for the event of 774 and some other years, there is data on supernova explosions. On the other hand, some of the events, it seems, could not be associated with supernovae. Perhaps the nature of the peaks of carbon-14 accumulation is more complicated than it seemed so far.
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