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November 2003
Kuiper belt: Far Removed
The first Kuiper-belt object was discovered only a decade ago, after a long search. In the 1950s, Kuiper and Edgeworth predicted a region beyond Neptune filled with small, icy bodies. Now nearly 1,000 such objects are known, and many astronomers consider that Pluto is not a true planet but a Kuiper-belt body discovered 60 years before its time. One remaining puzzle about this distant region of the Solar System is the lack of mass in the 'dynamically cold' Kuiper belt, bodies in low-inclination orbits about 50 astronomical units (7 billion km) from the Sun. Levison and Morbidelli have developed a model that explains Kuiper-belt formation and is consistent with the conditions we observe. They conclude that the entire Kuiper belt formed closer to the Sun that it is now and was transported outwards during the final phase of planet formation.
The formation of the Kuiper belt by the outward
transport of bodies during Neptune's migration
HAROLD F. LEVISON & ALESSANDRO MORBIDELLI
Nature 426, 419–421 (2003); doi:10.1038/nature02120
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Planetary science: Conveyed to the Kuiper belt
RODNEY GOMES
The small icy bodies that make up the Kuiper belt are the most distant
objects known in the Solar System. A consistent picture is now emerging
which suggests that these objects formed much closer to the Sun.
Nature 426, 393–395 (2003); doi:10.1038/426393a
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