Study Suggests the Sun May Be Due for a Powerful Superflare

The Sun is far from tranquil. Its surface churns with convection, its magnetic field continuously snaps and reconnects, and it releases energy through violent flares and plasma bursts known as coronal mass ejections (CMEs).

Most solar activity poses little threat to Earth, but occasionally, the Sun erupts with a flare so powerful it can cause significant damage. Unfortunately, scientists still don’t know exactly how often such events occur. Estimates range from once a century to once every thousand years.

A new study, however, suggests the lower end of that scale might be closer to the truth. By analyzing the eruption rates of 56,400 Sun-like stars, researchers have estimated that the Sun could produce a superflare approximately once every 100 years. If accurate, this raises concerns—especially since the infamous Carrington Event of 1859, which disrupted global telegraph systems, was only 1% as intense as a superflare.

“We were very surprised,” notes astronomer Valeriy Vasilyev of the Max Planck Institute for Solar System Research, “that Sun-like stars are prone to such frequent superflares.”

Understanding how often the Sun emits such colossal bursts of radiation is a challenge. Scientists can’t replay past events, and indirect evidence—like spikes in carbon-14 found in tree rings or nitrogen traces in polar ice—provides only partial insights.

Refining Estimates with G-Type Yellow Dwarf Stars

To refine their estimates, researchers turned to G-type yellow dwarf stars, which are similar to our Sun, and monitored them for flare activity. However, measuring these stars’ rotation rates—a factor likely tied to flare frequency—is not always straightforward.

Recognizing this limitation, Vasilyev and his team expanded their study to include stars with unknown rotation rates but similar brightness and temperature to the Sun. They also excluded stars with rotation periods under 20 days, since faster rotation generally indicates younger, more active stars. The Sun’s rotation period, by comparison, is 25 days.

By analyzing a sample of 56,450 Sun-like stars, the team observed 2,889 superflares across 2,527 stars. Their findings suggest a superflare rate of roughly once every century.

What does this mean for the Sun? While its behavior remains uncertain, we know it can unleash powerful disruptions. The Carrington Event of 1859, for instance, included both a solar flare and a CME that caused a massive geomagnetic storm on Earth. This storm overloaded telegraph systems worldwide, sparking fires and creating auroras visible near the equator.

Understanding Geomagnetic Storms: From 1989 Blackouts to Ancient Miyake Events

More recently, a geomagnetic storm in 1989 disrupted power grids, leading to widespread blackouts. Even more extreme events, known as Miyake events, have been identified through tree ring records. These superstorms, significantly stronger than the Carrington Event, have occurred nine times in the last 15,000 years, with the most recent in 774 CE. However, not all solar flares are accompanied by CMEs, and the relationship between superflares and these extreme particle events remains unclear.

“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,” explains astrophysicist Ilya Usoskin of the University of Oulu in Finland. “This requires further investigation.”

Solar flares alone can disrupt high-frequency radio communications by altering the ionosphere, but CMEs pose a much larger risk. They generate ground currents that can overload power grids and damage infrastructure. The best defense against these events lies in accurate forecasting, which requires a deeper understanding of the Sun’s behavior.

“The new data are a stark reminder that even the most extreme solar events are part of the Sun’s natural repertoire,” says astrophysicist Natalie Krivova from the Max Planck Institute for Solar System Research.

As researchers continue to unravel the mysteries of solar activity, one thing is clear: preparing for the Sun’s natural, albeit infrequent, outbursts is more important than ever.

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