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Tree Rings May Reveal Evidence of Supernova Activity


New research by geoscientist Robert Brakenridge of the University of Colorado at Boulder shows that three rings may contain evidence of massive space explosions. When a huge star dies, it emits high levels of gamma radiation into the cosmos. However, these colossal explosions don’t just affect space. In addition, they also leave permanent records on Earth’s geology. A study from November 4, 2020 in International Journal of Astrobiology reveals that plants can keep records of these heavenly explosions.

“These are extreme events, and their potential effects appear to match the tree-ring records,” explained geoscientist Robert Brakenridge of the University of Colorado Boulder.

The study looks at the effects of supernovae, which astrophysicists describe as some of the most violent events in outer space. To get an idea of ​​the magnitude of one of these explosions, imagine this. A single supernova explosion can release as much energy in a few months as the Sun does throughout its lifetime. Not surprisingly, supernovae also emit a large amount of light into space.

Brakenridge, a senior research associate at the Institute for Arctic and Alpine Research (INSTAAR) at CU Boulder, further noted the following:

“We see supernovae in other galaxies all the time. Through a telescope, a galaxy is a small hazy point. Then all of a sudden a star appears and it can be as bright as the rest of the galaxy. “

Scientists don’t know exactly how often these supernova explosions occur in our galaxy. Several studies estimate that one to three supernovae occur every century. However, records show that the most recent one exploded more than 400 years ago. A supernova explosion that occurs near Earth could easily end human civilization. However, even if they explode further, the supernova can still damage our ozone layer. In addition, it emits dangerous levels of radiation, although not enough to completely annihilate us.

Scientists have a hard time detecting supernovae as their brightness varies over time. However, Brakenridge and his team thought that looking a little closer to Earth could yield some evidence of these explosions. They decided to look through Earth’s tree ring records in hopes of finding evidence of supernovae. Their findings revealed that relatively close supernovae could have caused at least four climatic disturbances on Earth in the past 40,000 years.

Radiocarbon is the key to understanding supernova activity.

Brakenridge explained that radiocarbon, an isotope of carbon found in minute quantities on Earth, provides evidence for supernovae. Radiocarbon is only formed when cosmic rays from outer space frequently penetrate our atmosphere. Since this radiation is constantly produced in space, the Earth always receives a dose in varying amounts. When these cosmic rays enter the upper atmosphere, they collide with nitrogen atoms, producing a nuclear reaction that results in radiocarbon.

“There is generally a constant amount year after year,” Brakenridge said. “The trees collect carbon dioxide, and part of that carbon will be radiocarbon. “

However, the radiocarbon recorded in trees varies according to cosmic events. Scientists hypothesize that solar flares and storms can explain random spikes in this isotope that occur over several years and then fade away again. Brakenridge and his team believe that these radiocarbon spikes may occur due to much more distant space activity.

“There are really only two possibilities: a solar flare or a supernova,” he said. “I think the supernova hypothesis has been discarded too quickly.”

The study

To test his theory, he and his team analyzed tree-ring records. The first compiled a list of supernovae recorded in the last 40,000 years, as observed in the remains of stars. The scientists then compared this list to records of radiocarbon spikes that occur in tree rings over the same time period.

They found that unexplained spikes in radiocarbon levels corresponded to the right closest supernova to Earth.

The team focused on four that stood out the most:

  1. The Vela supernova, once 815 light years from Earth, exploded about 13,000 years ago. The tree ring records showed a 3 percent increase in radiocarbon about the same time. However, the date of the Vela explosion could have occurred 1,500 years later or earlier, as scientists can only estimate the timing.
  2. the 3 + 00.3 The supernova exploded about 7,700 years ago. It once sat at a distance of about 2,300 light years from Earth and corresponded with a 2 percent increase.
  3. Vela Jr. could have occurred 2,800 years ago, although scientists have a hard time pinning down the exact time. It corresponded to a radiocarbon peak of 1.4 percent.
  4. Finally, HB9, which exploded 5,400 years ago 1,000 to 4,000 light-years from Earth, caused a 0.9 percent increase in radiocarbon.

While researchers can’t yet extract conclusive evidence from tree rings, the evidence so far looks promising. Their main difficulty lies in accurately dating supernovae, but Brakenridge believes the findings so far warrant further investigation. Brakenridge said:

“What keeps me going is when I look at the terrestrial record and say, ‘Oh my God, the predicted and modeled effects seem to be there.’

If they can find more accurate ways to date supernova activity, the tree rings could provide a great insight into these celestial events. So perhaps we can learn more about any supernova that may threaten Earth soon.

Brakenridge hopes that humanity will not have to deal with any explosive stars anytime. However, some astronomers believe they have found evidence that Betelgeuse, a red giant star in the constellation Orion, could soon explode. It is located only 642.5 light years from Earth, which is much closer than Vela. However, no studies or findings on this hypothesis have yet been published.

“We can hope that is not what is going to happen because Betelgeuse is very close,” he said.

Final thoughts on what tree rings can reveal

Scientists have discovered that tree rings may contain clues from the past supernova activity. A CU Boulder geoscientist believes that the radiocarbon peaks in the tree rings correspond to known supernovae in the last 40,000 years. While the research linking these events is still in its infancy, it could help scientists analyze supernova activity more extensively in the future.



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