Sun-like stars said to emit superflares

The sun

AUSTIN, Texas (AP) -- Superflares powerful enough to fry nearby planets regularly erupt from distant stars that are just like the sun, but such death-dealing explosions are unlikely to occur in our solar system, astronomers say.

Two Yale University researchers said Wednesday that they have found nine solar-type stars that have erupted in flares up to 10 million times more powerful than anything ever recorded from the sun. There is preliminary evidence for at least seven others, they said.

If the sun were to have such an eruption, said Bradley E. Schaefer, it could possibly cause mass extinctions, plunge the Earth into brief heat wave, flood the planet with gamma and X-rays, melt electronics in orbiting satellites, cause global auroras and wipe out for up to two years all of the ozone that protects the Earth from harmful ultraviolet radiation.

"The loss of ozone could kill the food chain and probably cause mass extinctions," Schaefer said.

Even smaller bursts, he said, could burn out all of the electricity distribution systems on Earth, plunging the planet into a global power outage.

But the Yale professor said there is no evidence that such powerful "superflares" have ever erupted from the sun.

"It's not going to happen here," Schaefer said repeatedly in a presentation at the national meeting of the American Astronomical Society.

Schaefer said that an examination of astronomy archives uncovered proof that superflares erupt about once a century from G type, main sequence stars, the stellar type that is just like the Earth's own sun. The erupting stars are up to 100 light years away and pose no threat to the Earth.

"We found that superflares do occur on disturbingly normal solar-type stars," said Schaefer. "Superflares are 100 to 10 million times more energetic than the brightest solar flares."

He said the superflares last for one hour to one week and cause the stars to brighten by to 1,000 times their normal luminosity.

Schaefer said he believes the sun will never erupt with such powerful flares because there is no evidence that it has ever happened during the 4 billion year history of the sun.

The sun has been scientifically studied for more than 150 years and the most powerful solar flares detected have been only a fraction of energy in superflares, he said.

Additionally, astronomy records going back for 2,000 years have never recorded a superflare from the sun, said Schaefer. And, furthermore, such a superflare would have melted the ice on the moons of Jupiter and left smooth frozen plains. Recent spacecraft pictures of the moons show no such evidence, he said.

Eric P. Rubenstein, another Yale astronomer, said the eruptions probably occur because the distant stars have Jupiter-sized planets in a very close orbit.

Giant planets in orbit close to a star, he said, would cause a twisting and stretching of the magnetic fields that radiate out from stars and from most planets. The twisted magnetic field lines eventually would explode with a sudden release of energy.

He said his proposed superflare process is rather like what happens when rubber bands are twisted and twisted until they finally break and snap. The result is a sudden release of energy.

Rubenstein said that if his theory is correct, it would explain why the sun has never had a superflare. Jupiter and Saturn do have strong magnetic fields, but the giant gaseous planets are both too far out to interact powerfully with the magnetic field of the sun, he said.