Every so often, the Sun throws such a furious tantrum that it hurls highly damaging radioactive atoms towards Earth. These so-called ‘superflares’ release more than one octillion (1,000,000,000,000,000,000,000,000,000) joules of energy in one go – that’s like 16 trillion trillion atomic bombs detonating simultaneously.
New research suggests that solar tantrums happen far more frequently than we thought, and there’s no telling when another might happen.
Published in the journal Science, the study reveals that the Sun was at its most violent in 775 AD, with as many as eight other extreme solar particle events happening within the past 12,000 years.
But the study also suggests we could be underestimating the frequency and violence of these, based on other stars in the Universe. Previous research estimated that superflares happen every thousand to ten thousand years – but this new data brings that estimate far higher. In fact, the researchers now think one Sun-like star produces a superflare about once per century.
Though the magnetic field protects us from severe radiation, the authors behind the study warn that another solar tantrum could have severe impacts for life on Earth.
“The new data are a stark reminder that even the most extreme solar events are part of the Sun's natural repertoire,” said co-author Dr Natalie Krivova from the Max Planck Institute for Solar System Research, Germany.
The scientists collected existing evidence of the Sun’s superflares from ancient tree trunks and glacial ice from millennia ago, as well as analysing levels of radioactive atoms. But when it comes to direct data, what’s available is only as old as the start of the space age.
So, to get a better sense of longer-term frequency, the international team of researchers studied thousands of Sun-like stars (in terms of temperature and brightness) and recorded fluctuations in their brightness between 2009 and 2013 using data from NASA’s space telescope Kepler.
The most precise study yet, observations of the 56,450 Sun-like stars gave a total of 220,000 years of evidence – evidence revealing that 2,527 of these produced a total of 2,889 superflares during that time.
“We were very surprised that Sun-like stars are prone to such frequent superflares”, said first author Dr Valeriy Vasilyev.
In 1859, during one of the most violent solar storms to hit Earth over the past two centuries, the telegraph network collapsed across Europe and the USA. That solar storm was only one-hundredth of the energy released during a superflare.
The researchers caution that our infrastructure on Earth as well as satellites could be at risk. However, future missions like ESA’s Vigil probe, due to launch in 2031, could help to provide such an early-warning system.
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