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[Music]

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[Music]

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I'm Aki Roberge,

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an astronomer at NASA's Goddard Space Flight Center. I've been studying

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a young nearby planetary system around the bright star Beta Pictoris.

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Located 63 light-years away, and only about

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20 million years old. the star is surrounded by a vast disk of

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gas, dust and comet-like bodies that we view edgewise.

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We know of one planet in there too, it's a giant planet tracking along

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an orbit nearly as large as Saturn's. I'm part of a team

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studying Beta Pic's disk using the ALMA observatory in Chile.

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We've found something odd: a belt of carbon monoxide

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gas centered about three times farther from the star than Neptune's

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distance from the sun. The total amount of gas is about

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one-sixth the mass of all the water in Earth's oceans. What's

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interesting is that incoming ultraviolet light should break up the carbon

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monoxide molecules in little more than a century, on average.

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This means that the carbon monoxide must be resupplied by the breakup of icy

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comets. To produce the amount of gas we detect, we're looking at the

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equivalent of the total destruction of a large comet every 5 minutes.

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From our data, we can tell that much of the carbon monoxide

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is in one or two massive clumps, which was very surprising.

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Because we're viewing the disk edge-on, we can't be sure if its one or

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two. Regardless, the comets suppling the gas must also

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be concentrated into clumps. How could this happen?

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If there is one clump, we think we're seeing the aftermath of collision

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between two icy planets about the mass of Mars.

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Such a collision would have occurred about half a million years ago, releasing large

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quantities of gas and small, comet-like fragments.  The second

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--and we think more likely--scenario is that the carbon monoxide

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exists in two clumps and is continually replenished by by collisions in

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huge comet swarms. We believe the comets are shepherded together

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by an as-yet-undetected second planet whose gravity confines

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the comets into a small region so the frequently collide. A planet

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with roughly Saturn's mass could do the job. Other observations

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hint that the brightest clump is moving in a way that makes the two clump

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scenario more likely. Further observations will track it in better detail

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and help us confirm this dramatic picture.

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