StarDate 5/1/2014: Young Planets On The Move

by Damond Benningfield
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FROM THE UNIVERSITY OF TEXAS McDONALD OBSERVATORY, AS HEARD ON KCBS RADIO WEEKDAYS @ 9:52 A.M., 7:35 P.M. & 2:52 A.M.

STARDATE 5/1/2014:  Young planets are on the move — they may be born far from their stars but quickly move closer. Some may get too close — they may fall into the star and be destroyed.

Astronomers at McDonald Observatory are trying to find out how often young planets wander so dramatically. They’re looking for giant planets in distant orbits — arrangements that are similar to our own solar system.

Most of the planets discovered in other star systems are quite close in. That includes many planets that resemble Jupiter, the giant of the solar system.

But there’s a problem with that layout.

Giant planets probably grow so large by first amassing chunks of rock and ice to build a heavy core. The gravity of that core then quickly sweeps up vast amounts of gas left over from the star’s birth.

But a star’s heat and winds prevent that process from playing out close to the star itself. So a giant planet must form away from the star, where it’s colder. Interactions with the remaining gas and with other planets may slow it down, causing it to spiral closer. Small planets that are born close to the star may even fall into it.

The McDonald project is trying to determine how common it is for giant planets to remain far from their stars. The astronomers can then look for a common factor that may allow giant planets to remain far away. That will provide a better understanding of the evolution of all planetary systems — including the ones where the young planets don’t stay at home.

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