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Study: Big planets form in cosmic flash

By Richard Stenger
CNN

Artist's concept of an exoplanet
Artist's concept of an exoplanet

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PLANET FINDERS

(CNN) -- Giant gas planets like Jupiter probably form in hundreds of years, not millions of years as had been commonly thought, according to a new report.

The jovian giants must sprout hastily in order to survive the punishing rays of nearby stars, an international team of astronomers said.

If the growth process takes too long, the stellar radiation would heat and disperse the vast gas reserves accumulating around the cores of large planets.

"If a gas giant planet can't form quickly, it probably won't form at all," said University of Washington physicist Thomas Quinn, co-author of a study in the November 29 issue of the journal Science.

Many researchers had believed that planets as large as Jupiter formed over eons from the debris rings that surround young stars. The planets were thought to congeal into cores over a million years or so, then gradually accumulate gas outer envelopes over another 1 million to 10 million years.

Spinning disks disintegrate

But Quinn and Lucio Mayer of the University of Zurich, using supercomputers to refine planetary formation models, found that spinning protoplanetary disks disintegrate after only a few revolutions.

As they break apart, matter soon clumps together and draws in surrounding gaseous debris.

"If these planets can't form quickly, then they should be a relatively rare phenomenon, whereas if they form according to this mechanism, they should be a relatively common phenomenon," Quinn said Thursday.

Astronomical observations in recent years suggest such planets are common, lending credence to the new research. In the last decade, one hundred or so planets have been detected around other stars, most as large or larger than Jupiter.

The new model needs additional work, Quinn and Mayer acknowledge. It does not explain why most so-called exoplanets orbit extremely close to their parents stars. Nor does it account for the formation of small, rocky inner planets like Earth and Mars.

With improvements in technology and search techniques, scientists using space- and ground-based telescopes expect to detect terrestrial-sized planets within a decade or so.



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