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The enigmatic icy rocks known as the Kuiper Belt came to inhabit the distant fringes of the Solar System thanks to the gravitational pull of youthful Neptune billions of years ago, a study says. The Kuiper Belt is a disk-shaped region beyond the orbit of Neptune that is inhabited by tens of thousands of icy bodies which, for some theorists, include Pluto, whose status as a genuine planet is in doubt, and may also be the source of some kinds of comets. But the Belt has raised questions ever since it was identified in the 1950s by US-Dutch astronomer Gerard Kuiper as some of the rubble left over from the building of the Solar System. One of them is that the Belt has too little mass to be in its far-flung location. Either it has lost mass over time, or it was created closer to the Sun and moved. Writing in Thursday's issue of the British weekly journal Nature, Harold Levison of the Southwest Research Institute at Boulder, Colorado, and Alessandro Morbidelli of France's Observatoire de la Cote d'Azur in Nice work back to the infancy of the Solar System. In its primordial state, the Solar System comprised the Sun and the nascent planets -- accumulations of gas and dust that consolidated into gradually larger masses. The fledgling planets were surrounded by a vast orbiting ring of asteroid-sized bodies called planetesimals, circling about five billion kilometers (three billion miles) from the Sun, according to the duo's theory. The gravitational pull of this huge ring was such that the young planets, with the exception of Jupiter, were gradually pulled away from the Sun. As their orbits expanded, the planets gathered further mass from the whirling dust and rocks, and their gravitational force in turn affected the orbit of the planetesimals. Eventually, a remnant of the planetesimals, pushed notably by Neptune -- by now a gaseous giant -- ended in the present location of the Kuiper Belt, about seven billion kilometers (4.4 billion miles) from the Sun. "The original Kuiper Belt region could in fact have been virtually empty and subsequently only a small amount of mass was deposited there," said Rodney Gomes, of the Federal University of Rio de Janeiro, Brazil, in a commentary. All rights reserved. � 2004 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse. Quick Links   Nov 02, 2006 |
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