To be clear, Proxima Centauri is not like the Sun. It’s an M dwarf, a diminutive orb that glows red. And these tiny stars are famous for their oversized flares. But some Sunlike stars can send up super flares as well.
This realization has come from telescopes in space designed to look for planets around other stars. NASA’s now-defunct Kepler telescope did this by looking for subtle dips in starlight as planets crossed in front of their suns.
Over four years, Kepler recorded 26 super flares — up to about 100 times as energetic as the Carrington Event — on 15 sunlike stars, researchers reported in January. NASA’s ongoing TESS mission, another space-based telescope hunting for exoplanets, found a similar frequency of superflares on Sunlike stars in its first year of operation.
The Kepler data imply that Sunlike stars experience the most powerful of these flares roughly once every 6,000 years. Our Sun’s most powerful eruption in that time span is an order of magnitude weaker — but could a super flare be in our future?
“I don’t think any theory has sufficient predictive capability to mean anything,” Hudson says. “The leading theory basically says that the bigger the sunspot, the greater the flare.” Sunspots mark where the Sun’s magnetic field punches through its surface, preventing hot gas from bubbling up from below. The spot looks dark because it’s cooler than everything around it.
And that is one difference between the Sun and its eruptive neighbors. Super flares seem to happen on stars with cool, dark spots far larger than ever appear on the Sun. “Based on known spot areas, there would therefore be a limit,” Hudson says.
The intricacies of any star’s magnetic machinations — spots, flares, etc. — are still poorly understood, so tying all these observations into one cohesive story will take time. But the quest to understand all this might improve predictions about what to expect from the sun in the future.
Flares that are powerful enough to disrupt our power grid probably occur, on average, a few times a century, Love says. “Looking at 1859 kind of helps put it in perspective, because what’s happened in the space-age era, since 1957, has been more modest.” The Sun hasn’t aimed a Carrington-like flare at us in quite a while. A repeat of 1859 in the 21st century could be disastrous.
Humanity is far more technologically dependent than it was in 1859. A Carrington-like event today could wreak havoc on power grids, satellites and wireless communication. In 1972, a solar flare knocked out long-distance telephone lines in Illinois, for example. In 1989, a flare blacked out most of Quebec province, cutting power to roughly 6 million people for up to nine hours. In 2005, a solar storm disrupted GPS satellites for 10 minutes.
The best prevention is prediction. Knowing that a coronal mass ejection is on its way could give operators time to safely reconfigure or shut down equipment to prevent it from being destroyed.
Building in extra resiliency could help as well. For the power grid, that could include adding in redundancy or devices that can drain off excess charge. Federal agencies could have a stock of mobile power transformers standing by, ready to deploy to areas where existing transformers — which have been known to melt in previous solar storms — have been knocked out. In space, satellites could be put into a safe mode while they wait out the storm.
The Carrington Event was not a one-off. It was just a sample of what the sun can do. If research into past solar flares has taught us anything, it’s that humanity shouldn’t be wondering if a similar solar storm could happen again. All we can wonder is when.
10.1146/knowable-091721-1
Christopher Crockett is a staff researcher for Knowable and a freelance science writer living in Arlington, Virginia. He is thankful for the sun but wouldn’t want to see it when it’s angry.
This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.