Solar flares were once thought to be to blame for historical radiation spikes on Earth.
However, a new study suggests that those radiation spikes were not caused by solar flares, as previously thought, implying that something much more powerful - and still unknown to us - was responsible instead.
Unknown Threat
Solar Dynamics Observatory via Getty Images
There is an extreme astrophysical phenomenon that we don't understand, and it could pose a threat to us, according to Benjamin Pope, coauthor of the study and astrophysicist at the University of Queensland, as per Futurism.
The study, published on Wednesday in the Proceedings of the Royal Society A, looked for spikes of carbon 14, a radioactive isotope of carbon whose increased presence corresponds to increases in radiation levels on Earth.
The radiation increases are caused by mysterious astrophysical events known as "Miyake events," after the Japanese scientist discovered them.
According to Pope, six known Miyake events have occurred in the last 10,000 years, with the most recent occurring in 993 CE.
They were previously thought to be caused by severe solar storms that typically occurred at the solar cycle's 11-year peak of sunspot activity.
However, after analyzing the data, Pope and his colleagues discovered that these radiation spikes occurred throughout the solar cycle, not just at its 11-year peak, throwing a wrench in the prevailing theory.
Even stranger is the duration of some of the spikes.
According to Pope, at least two, possibly three of these events took more than a year, which is unusual because a solar flare would not take that long.
The most powerful solar flare to hit our planet was in 1859.
The Carrington Event, as it was known at the time, severely damaged telecommunications infrastructure.
A Carrington-like event today could be far more devastating, given our reliance on electronics and the internet.
However, whatever caused the Miyake events were potentially 100 times more powerful than even the Carrington.
Many tree species, particularly those in temperate climates, lay down a new ring every year that acts as a barcode for their age, as per ABC News.
These time markers also assisted scientists in determining when the tree absorbed radioactive carbon-14, which was produced by the interaction of high energy particles emitted by cosmic rays and solar storms interacting with the atmosphere.
Sunspot activity peaks every 11 years, making strong solar storms four times more likely.
Benjamin Pope, an astrophysicist at the University of Queensland, wanted to examine all tree ring studies to determine how strong the Miyake events were and when they occurred in the solar cycle.
He tasked his undergraduate students, led by Qingyuan Zhang, with creating a program that would crunch all of the data ever published on the events and model how carbon had been locked up in tree rings as it cycled through Earth's biosphere over the past 10,000 years.
"We just thought it would be very interesting if we could confirm or challenge some of the existing hypotheses about the origin of Miyake events," Mr Zhang said.
The study's data revealed that these mysterious radiation storms occurred roughly once every 1,000 years and occurred throughout the solar cycle, not just at solar maximum.
Many of the spikes were more intense than typical solar storms. One event in 663 BC lasted up to three years, and another in 5480 BC lasted a decade.
