The sun could be one of our biggest threats in the next 100 years. If an enormous solar flare like the one that hit Earth 150 years ago struck us today, it could knock out our electrical grids, satellite communications and the internet. A new study finds that such an event is likely within the next century.

“The sun is usually thought of as a friend and the source of life, but it could also be the opposite,” says Avi Loeb at Harvard University. “It just depends on circumstances.”

Loeb and Manasvi Lingam, also at Harvard, examined data on other sun-like stars to see how likely solar “superflares” are and how they might affect us.

They found that the most extreme superflares are likely to occur on a star like our sun about every 20 million years. The worst of these energetic bursts of ultraviolet radiation and high-energy charged particles could destroy our ozone layer, cause DNA mutations and disrupt ecosystems.

But in the shorter term, the researchers say that less intense superflares of a type we know can happen on our sun could still cause problems. In 1859, a powerful solar storm sent enormous flares towards Earth in the first recorded event of its kind. Telegraph systems across the Western world failed, with some reports of operators receiving shocks from the huge amounts of electrical current forced through the wires.

Tech wipeout

“Back then, there was not very much technology so the damage was not very significant, but if it happened in the modern world, the damage could be trillions of dollars,” says Loeb. “A flare like that today could shut down all the power grids, all the computers, all the cooling systems on nuclear reactors. A lot of things could go bad.”

Loeb says an event as powerful as the 1859 one could cause about $10 trillion of damage to power grids, satellites and communications. A flare just a bit stronger could even damage the ozone layer.

Previous work has shown that such an event seems likely to occur in the next century, with a 12 per cent chance of it happening in the next decade, but nobody seems to be all that worried, Loeb says. Asteroid impacts get all the attention when it comes to life-threatening space events, but Loeb and Lingam found that superflares would be just as deadly and are just as likely.

“I’m not lying awake in bed at night worrying about solar superflares, but that doesn’t mean that someone shouldn’t be worrying about it,” says Greg Laughlin at Yale University.

Last month, Loeb and Lingam came up with one potential way to protect Earth from superflares both large and small: an enormous loop of conductive wire between us and the sun that could act as a magnetic shield and deflect flares’ particles away.

Unfortunately, launching such a shield into space would cost upwards of $100 billion. “I think that seriously diverting resources to build a wire loop in space would not be the best way to spend money,” says Laughlin. “But thinking more about how solar superflares work and getting a sense of how our sun fits in with its peers would be a very valuable effort.”

Journal reference: The Astrophysical Journal, DOI: 10.3847/1538-4357/aa8e96