- 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 the solar system, astronomers say.
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- 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.
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- 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.
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- ``The loss of ozone could kill the food chain and probably
cause mass extinctions,'' Schaefer said.
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- Even smaller bursts, he said, could burn out all of the
electricity distribution systems on Earth, plunging the planet into a global
power outage.
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- But the Yale professor said there is no evidence that
such powerful ``superflares'' have ever erupted from the sun.
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- ``It's not going to happen here,'' Schaefer said repeatedly
in a presentation at the national meeting of the American Astronomical
Society.
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- 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.
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- ``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.''
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- 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.
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- 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.
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- 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.
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- 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.
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- Eric P. Rubenstein, another Yale astronomer, said the
eruptions probably occur because the distant stars have Jupiter-sized planets
in a very close orbit.
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- 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.
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- 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.
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- 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.
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