Busy Vega

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Busy Vega

A bright star crowns the sky this evening. Vega is the leading light of Lyra, the harp. It’s the fifth-brightest star in the entire night sky, so it’s hard to miss.

There’s a lot going on at Vega. The star itself is dynamic, and it’s encircled by a wide ring of dust — the likely aftermath of a big collision.

Vega is about twice the size and mass of the Sun. Perhaps because of its youth, though, the star spins more than a hundred times faster than the Sun does at the equator. That’s almost fast enough to rip the star apart. Instead, though, it causes Vega to bulge outward — it’s about 20 percent wider through the equator than through the poles.

Detailed observations have suggested that Vega’s brightness varies over a period of years — perhaps by a few percent. Different studies have come up with different results, though, so the matter isn’t settled.

Astronomers are sure that Vega is encircled by a wide disk of dust. It extends tens of billions of miles away from the star. Much of the dust probably resulted from the collision of two big asteroids or comets. The initial impact created a cloud of dust, plus several big fragments of the original bodies. They then had their own impacts, spewing more dust into space.

Vega could have planets as well as the dust. So far, there’s no solid evidence of any. But astronomers continue the search — looking for more activity in this busy star system.

More about Vega tomorrow.

Script by Damond Benningfield

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