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Crackling Star

April 14, 2015

Compared to the Sun, the star known as GJ 1243 is a dull ember. It’s about a quarter of the Sun’s size and mass, but less than one percent as bright. Yet there’s one way in which it puts the Sun to shame: It produces more of the powerful explosions known as flares, which can be stronger than anything from the Sun.

GJ 1243 is a red dwarf. These tiny stars outnumber all the other classes of stars put together. But because they’re the least-massive stars, their light is feeble — not a single one is visible to the unaided eye.

Because of its size, though, a red dwarf behaves a little differently from stars like the Sun. All of the gas outside its core is like a big pot of boiling water, with gas circulating between the core and the surface.

That generates a powerful magnetic field, which in turn produces big “starspots” — magnetic storms on the star’s surface. The activity also produces flares — powerful outbursts of particles and energy.

Astronomers used the planet-hunting Kepler space telescope to keep an eye on GJ 1243 for 300 days. They found that about three percent of the star’s surface was covered by starspots — a far larger percentage than on the Sun. And they detected more than 6,000 flares — more than have been seen on any star other than the Sun. Many of the flares were small, but quite a few were stronger than any solar flares — making this faint star crackle like a Fourth-of-July fireworks display.


Script by Damond Benningfield, Copyright 2015

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