Whenever the sun throws out a big solar storm, we’ve got the observatories and telescope to monitor it closely. Even storms that happened a few centuries ago are recorded in tree rings and isotopes. But if you want to go back long enough, to thousands of years, the records are way more murky.
This leaves us with a limited perspective. If we had detailed records stretching back millennia, we’d know how often such storms occur. But with current records, we can’t accurately determine how frequently our star exhibits these cosmic outbursts.
To get around this problem, a team of scientists from across the globe decided to look at other stars resembling our own to keep tabs on their furiousness and compare them to our home star.
“We cannot observe the Sun over thousands of years,” said Max Planck Institute for Solar System Research (MPS) director Sami Solanki. “Instead, however, we can monitor the behavior of thousands of stars very similar to the Sun over short periods of time. This helps us to estimate how frequently superflares occur.”
In a new study published in Science, researchers examined brightness data collected by NASA’s Kepler telescope between 2009 and 2013. Altogether, these measures provided a vast observational baseline.
“In their entirety, the Kepler data provide us with evidence of 220,000 years of stellar activity,” said Alexander Shapiro from the University of Graz.
In other words, while Kepler only observed each star for a few years, combining data from thousands of Sun-like stars provided an equivalent of 220 millennia of stellar activity. This extensive sample allowed scientists to make more confident conclusions about the frequency of massive flares on stars similar to the Sun.
Zooming in on Sun-like stars
They focused on 56,450 stars closely matching the Sun’s temperature and brightness. From these stars, the team carefully singled out 2,889 extremely strong flares—known as superflares—on 2,527 stars.
The results were stunning.
“We were very surprised that sun-like stars are prone to such frequent superflares,” said first author Valeriy Vasilyev from the MPS.
Each superflare was more intense than any flare observed on the Sun in recent decades. Previously, scientists believed such events were rare, occurring maybe once every thousand years or more. This study suggests they might actually occur once per century. This raises important questions about how these superflares relate to major solar storms that impact Earth.
Natural records on Earth, such as isotopes in tree rings and ice cores, suggest major solar storms are rarer. Using this method, scientists have identified five extreme solar particle events and three potential candidates within the past 12,000 years of the Holocene epoch. This averages to about one event every 1,500 years. The most intense event is believed to have occurred in 775 AD. However, it’s possible that more superflares and violent particle events occurred in the past but left no detectable trace.
“It is unclear whether gigantic flares are always accompanied by coronal mass ejections and what is the relationship between superflares and extreme solar particle events,” said Ilya Usoskin from the University of Oulu in Finland.
In other words, not every superflare may produce the energetic particles that leave a clear signature in Earth’s natural archives.
For us, understanding these events is important. The “Carrington event” of 1859, one of the most powerful solar flares in the past two centuries, knocked out telegraph lines throughout large parts of northern Europe and North America. A stronger superflare could potentially damage satellites, communication networks, and power grids in today’s technology-based world.
Scientists cannot say when the next large solar outburst will occur, but they are working on new ways to prepare. Looking ahead, better solar monitoring and early-warning spacecraft—like ESA’s Vigil mission—could provide timely heads-ups if our star ever decides to unleash a giant outburst. With these findings, scientists now have a clearer understanding of just how frequently stars like the Sun might throw energetic fits—and what that could mean for our technologically dependent society.
