- Supernovae that occurred thousands of years ago left traces on Earth;
- A study showed that tree rings hold marks from these explosions;
- Scientists observed sudden spikes in Carbon-14 concentration in some rings;
- This increase may be associated with supernova explosions in the interstellar neighborhood.
Imagine if, overnight, a new celestial body appeared in the sky, brighter than all the stars and visible even during the day.
It is a violent explosion that occurs when massive stars reach the end of their lives. To give you an idea, a supernova can release in a few months the same energy that the Sun releases throughout its life cycle.
If a supernova occurs in the wrong place – too close to Earth – it could be the end of life here.
New research by geologist Robert Brakenridge of the University of Colorado Boulder (USA), however, found that even distant supernovae can leave traces on our planet, exposing us to radiation, damaging the ozone layer, and possibly affecting our climate.
The study was based on the observation of tree rings and the levels of carbon-14 found in them.
Carbon-14 (or radiocarbon) is a slightly radioactive isotope of carbon that exists in small amounts on Earth and is formed when cosmic rays reach our atmosphere, which occurs constantly.
Trees absorb carbon dioxide, and part of it is carbon-14. What is normally seen in tree rings is a gradual increase in this isotope.
Sometimes there are sudden spikes in the concentration of carbon-14, something that has yet to be explained.
There are really only two possibilities: A solar flare or a supernova. I think the supernova hypothesis has been dismissed too quickly.Brakenridge said.
He compared the dates of the carbon-14 peaks in the tree rings with the supernovae that occurred more or less close to our planet in the last 40,000 years.
These events are identifiable by the traces they leave: nebulae, clouds of dust, and gases in space.
The observation indicates that supernovae could have generated at least four climatic disturbances on Earth in the observed period, and the eight supernovae that occurred closer to us seemed to be associated with such unexplained peaks in radiocarbon measurements.
One of these events was caused by the explosion of a star in the Vela constellation, about 13,000 years ago. Shortly thereafter, the levels of carbon-14 on Earth increased by 3%, a quite impressive amount.
Despite this, the results are still inconclusive because the dating of supernovae has a margin of error of up to 1,500 years.
Still, Brakenridge was able to prove that the effects that were predicted and modeled are present. He believes that the issue deserves greater attention from the scientific community.
Supernovae are extreme events, and their potential effects seem to match tree ring records.Brakenridge concluded.