Introduction

"Like gluttons whose hunger increases with age, some older stars similar to our own sun gobble up giant planets and other celestial bodies orbiting nearby," scientists reported on August 12, 1999.

THE TELLTALE SIGNS of stellar bingeing include bloating, lots of infrared light, a fast spin and traces of the element lithium, which is normally destroyed inside stars, researchers at the Space Telescope Science Institute reported. Our own sun will not get this hungry for 5 billion years or so, but astronomer Mario Livio found that as many as 100 million sunlike stars in the Milky Way galaxy have close-in gassy giant planets like Jupiter or failed stars called brown dwarfs orbiting around them. These planets and failed stars are likely to be devoured by the stars as they age.

As they age, stars like the sun expand into so-called red giants, engulfing any planets in close orbit. If these planets are as massive as Jupiter, they will make the gobbling star bigger and brighter as it absorbs the big planet's mass and thus increases its gravity. Scientists did not see any stars actually eating Ñ the planets were already being digested Ñ but observed the aftermath, which showed the stars heating up and blowing off expanding shells of dust, which radiate a lot of infrared light.

Not Our Sun's Fate

The stars also spun around faster after absorbing the planets, having taken in the orbiting companion's angular momentum. Big planets like Jupiter carry most of a stellar system's angular momentum. They also found evidence of the chemical lithium in the stars, which they theorized came from a newly devoured Jupiter-type planet. Our sun will not follow this path, simply because our solar system's gassy planets like Jupiter have orbits too far away from the sun to be engulfed this way. But new studies about possible planets outside our solar system show that gas giants can orbit close to sunlike stars. These planets, the statement said, "are doomed to be eventually swallowed and incinerated."

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