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Comets don't all start out on the fringe

New model suggests comets also come from the inner Oort Cloud

10:16am, January 6, 2010

WASHINGTON — A new study of fringe comets could let the outer solar system lose some weight.

Simulations of the most distant objects in the solar system suggest that, counter to long-standing thinking, the comets that swing past Earth can originate in the inner region of the Oort Cloud, not just from its outer fringes. The new model could resolve a discrepancy: The amount of solid mass estimated to have been in the protoplanetary disk falls short of the amount needed to build the Oort Cloud in the first place, said Nathan Kaib of the University of Washington. Kaib presented his calculations on January 5 at the winter meeting of the American Astronomical Society.

Comets were thought to come from only the outer Oort Cloud, a region that defines the edge of the solar system and is 20,000 times farther from the sun than is Earth. Being so remote from the sun, outer Oort Cloud objects can feel slight gravitational pushes from distant stars and the rotation of the M

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