Some Sun-like Stars Put Off Superflares
May 17, 2012

Some Sun-like Stars Put Off Superflares

New research shows that other sun-like stars in the universe can send off flares much larger than those seen on our sun.

Solar flares are the result of broken magnetic-field loops as they pass through sunspots. As these loops become twisted and contorted, the flares occur, sending enormous amounts of charged particles, energy and radiation outward. So far, the largest solar flare ever measured on our sun happened on September 1, 1859, by British astronomer Richard Carrington. He simply observed it as a mysterious brightening as he was drawing sunspots at the time.

Then, when the particles from the solar flare hit Earth just hours later, the magnetic shield was rocked, creating auroras in the sky. Telegraphy machines even threw off sparks when they were connected to their batteries.

Speaking to Nature, Bradley Schaefer of Louisiana State University in Baton Rouge said if such a flare were to occur today, the resulting power from it would “rock our transformers.”

Flares such as the one reported during the “Carrington Event” may be dangerous to Earth now, but flares even more powerful have been observed on other stars. These flares are reported to be 10 million times more energetic than our Sun´s largest flare and yet, observations of these superflares have been unreliable thus far.

Now, NASA´s Kepler spacecraft is in the sky, observing the same part of the universe continuously and keeping a safe distance as to catch one of these superflares as they occur.

“Suddenly the field is awash in huge amounts of data,” Schaefer said. “We´ve got a way to get good demographics on the stars that have superflares.”

So, with this data, Hiroyuki Maehara and colleagues at Kyoto University in Japan have conducted the first analysis of Kepler´s first 120 days in the sky when it launched in 2009. With this data, Maehara and team found there were 83,000 stars just like our sun. Of these, 148 threw off superflares with energies measuring 10 to 10,000 times greater than the Carrington Event.

The team expected the stars, which spin more quickly, to shoot off more solar flares. These stars did not disappoint as most of the 365 flares observed by the team came from these stars. What they found curious, however, was a quarter of the superflares they observed occurred on slower stars, much like our sun, which takes one month to complete its rotation.

Some astronomers blame the magnetic fields coming from nearby Jupiter-like planets. Instead of magnetic fields traveling from sunspot to sunspot, these fields could reach out and connect with nearby fields on these “hot Jupiter” planets, stretching and tightening as the sun-star orbits until the field is finally broken. The result is an explosive superflare which releases massive amounts of energy.

This may not, however, explain the superflares observed by Maehara and team, as no data from Kepler show any signs of a “hot Jupiter” nearby.

“It seems extremely unlikely that a planet is causing these flares,” says Lucianne Walkowicz, a Kepler team member at Princeton University in New Jersey. “More likely, it means that even when [stars are rotating slowly], they are occasionally able to store up their magnetic energy and release it in these big flares. It´s really a mystery as to how and why that happens.”

Luckily, astronomers don´t see superflares like this occurring on our sun´s surface. Maehara says our sun moves too slowly and its sunspots are too small to breed superflares. While a superflare could cause mass extinction events on Earth, Schaefer also says these superflares may be a sign of inhabitable life.

"Superflares might provide the high-energy radiation required to create organic molecules, so perhaps superflare systems are a good place to look for alien life that has evolved to avoid the effects of the huge flares," he said.