Our sun regularly shoots out solar flares — explosions of light and radiation from its surface — into space. But how about superflares?
These stellar events are thousands of times more powerful than typical solar flares, which can wreak havoc on our power and communication systems. To better understand the superflare risk from the sun, astronomers sought to find how often sun-like stars blast out such potent radiation, and to find an answer they surveyed a whopping 56,000 stars.
The results astonished them.
"Stars that are similar to our sun generate superflares once per century, which is 30 to 60 times more frequent than previously thought," Valeriy Vasilyev, a stellar activity researcher at the Max Planck Institute for Solar System Research in Germany, told Mashable.
"We were shocked by the high frequency," he said. Vasilyev is a co-author on the research published in the journal Science.
Previous research, for example, found that sun-like stars emit powerful superflares every 3,000 to 6,000 years.
To better understand the behavior of sun-like stars, which are relatively stable stars, astronomers used observations captured by NASA's now-retired Kepler Space Telescope. Kepler was designed to expertly measure stellar brightness as it searched for new planets transiting in front of their distant stars. The astronomers identified 56,450 stars that have sun-like characteristics, and over a four-year period spotted superflares — which show telltale signs of immediate light increases followed by a long tail of decaying light — on 2,527 sun-like stars. From this large number of superflares over a relatively brief time range, they inferred the frequency of how often these stars are blasting out superflares.
"We were shocked by the high frequency."
The distant stars emitted energies of some 10³⁴ to 10³⁶ erg ("erg" is a unit of energy measurement), which is greater than any flare ever observed from the sun. Such a superflare packs the energy of roughly 1 trillion hydrogen bombs, Vasilyev said.
"We found crazy flaring stars," he marveled.
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Solar flares explode from our star's surface when potent and changing magnetic fields naturally become tangled. "Like a rubber band that snaps when it is twisted too far, the tangled magnetic fields release energy when they snap," explains the University Corporation for Atmospheric Research. "The energy emitted by a solar flare is more than a million times greater than the energy from a volcanic eruption on Earth!"
And when solar flares shoot out on the side of the sun facing Earth, it can have consequences — particularly if it's a strong solar flare. Such mighty solar flares are often accompanied with events called "coronal mass ejections," or CMEs, which are massive ejections of super hot gas (like throwing a chunk of the sun into space).
Infamously, in 1989 a potent solar flare-associated CME knocked out power to millions in Québec, Canada. The CME hit Earth's magnetic field on March 12 of that year, and then, wrote NASA astronomer Sten Odenwald, "Just after 2:44 a.m. on March 13, the currents found a weakness in the electrical power grid of Quebec. In less than two minutes, the entire Quebec power grid lost power. During the 12-hour blackout that followed, millions of people suddenly found themselves in dark office buildings and underground pedestrian tunnels, and in stalled elevators." The same solar event fried a $10 million transformer at Salem Nuclear Power Plant in New Jersey.
Fortunately, Earth's protective magnetic field and atmosphere shield people from such harmful radiation. But this new research suggests we should be aware of the potential technological impacts from a superflare, which would be significantly more potent than the 1989 event. It remains unknown, however, if the sun has all the requisite properties of these distant sun-like stars that would stoke such relatively frequent solar flares.
Superflares don't just pose threats to Earth. They could impact the many planets orbiting other stars, called exoplanets. For instance, Vasilyev wonders what impacts radiation-heavy superflares might have on worlds with protective atmospheres thinner than Earth's.
But superflares aren't inherently bad. Conversely, superflares might provide the energetic kick molecules need to form the building blocks of life. Perhaps a lifeless Earth, in its distant past, even benefited from a superflare, or two.
