Extrasolar planets disappear after parent stars pluck them

April 28th, 2009 - 7:11 pm ICT by IANS  

Washington, April 28 (IANS) Billions of planets are orbiting stars outside our solar system, but many have disappeared after being plucked by the gravitational pull of their stars, according to a study.
Computer models over the last year or so have only predicted that gravitational forces might pull a planet into its parent star and this is such planet destruction has already occurred, said Washington University (WU) astronomer Rory Barnes.

“When we look at the observed properties of extrasolar planets, we can see that this has already happened - some extrasolar planets have already fallen into their stars,” he said.

Barnes, a researcher with the Virtual Planet Lab at WU, has co-authored a paper describing these findings. The research involves planets that are close to their parent stars. Such planets can be detected relatively easily by changes in brightness as their orbits pass in front of the stars.

But because they are so close to each other, the planet and star begin pulling on each other with increasingly strong gravitational force, mis-shaping the star’s surface with rising tides from its gaseous surface.

“Tides distort the shape of a star. The bigger the tidal distortion, the more quickly the tide will pull the planet in,” Jackson said.

Most of the planets discovered outside of our solar system are gas giants like Jupiter except that they are much more massive.

However, earlier this year astronomers detected an extrasolar planet which is significantly larger than our planet, but is more like Earth than any other extrasolar planet found so far, said a WU release.

That planet orbits only about 2.41 million km from its star, much closer than Mercury is to our sun, a distance that puts it in the category of a planet that will fall into its star.

These findings are slated for publication in the Astrophysical Journal.

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