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January 23, 2013

The Sun is a pretty sedate star — which is a good thing for life on Earth. It bathes us in life-giving light and heat. But it doesn’t zap us with the titanic explosions of energy seen on many other stars.

The Sun does produce outbursts known as solar flares. These eruptions can knock out orbiting satellites and trigger blackouts on the ground.

But recent observations by the Kepler spacecraft show that some stars launch superflares up to 10,000 times more powerful than any solar flare ever seen.

Kepler’s main task is to find planets that pass in front of their parent stars, blocking a bit of the star’s light. But because the craft is so sensitive to changes in stellar brightness, it can also detect superflares.

Japanese scientists studied Kepler observations of more than 83,000 stars that are similar to the Sun. During a four-month period, about 150 of these suns launched at least one superflare strong enough to damage the ozone layer of an Earth-like planet and produce a mass extinction.

Most of the superflares came from stars that spin much faster than the Sun does. Rapid rotation intensifies a star’s magnetic field, generating dark starspots and powerful flares. When the Sun was younger, it probably spun faster, too, so it may have produced its own superflares.

Today, the Sun spins slowly, so its magnetic storms are much less intense than those seen on other stars — keeping us safe from these stellar catastrophes.


Script by Ken Croswell, Copyright 2012

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