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After the supernova explosion, for at least several tens of thousands of years, its remains are visible: an expanding cloud of gas. By studying the movement of gas, temperature and other properties, astronomers can also determine the timing of a supernova explosion.
It is known that in the past 40,000 years at least 18 supernovae have exploded less than 1,500 parsecs from Earth. Their gamma radiation, reaching the earth’s atmosphere, may have knocked down some nitrogen atoms and converted their nuclei into radioactive carbon.
Wood groove
Carbon, both conventional and radioactive, is incorporated by living organisms, including trees, so changes in the abundance of radioactive carbon are reflected in their grooves. Several sudden changes in the abundance of radioactive carbon in Earth’s atmosphere have long been known in the past, but so far no attempt has been made to link them to the timing of specific supernova explosions.
This is exactly what the new study has done. Of the 18 supernova explosions, eight left identifiable traces of radioactive carbon in the furrows of trees, and four traces were truly significant, surpassing the percentage. The largest peak, also a three percent increase, occurred 12,800 years ago.
Interestingly, it was then the beginning of global warming on Earth, called the Younger Dryas. Whether it was caused by the explosion of a comet that left Velha’s remains, we cannot answer for sure, but this study shows that such a hypothesis is at least plausible.
The study results are published in the International Journal of Astrobiology; a publicly available version (as if it were a little earlier) of the article can be found in arXiv.
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