Asteroids, Comets, and Meteoritesate-period and long-period comets appear to originate from the Oort cloud, whereas the Jupiter-family comets appear to come from the Kuiper belt. The comets might have originally traveled in large, randomly oriented orbits similar to the long-period comets.They might have been diverted into a flat ring by the gravitational attraction of the large outer gaseous planets, principally Jupiter. However, Jupiter gravity appears too weak to transform long-period comets from the Oort cloud efficiently into short-period ones. Therefore, the probability of gravitational capture seems too remote to account for the large number of short-period comets that tend to lie in planes close to the ecliptic. Apparently, the disk of the solar system does not abruptly end at the orbits of Neptune and Pluto, which swings in and out of Neptune orbit but avoids collision by a quirk of orbital geometry.This feature lends credence to the idea that Pluto, whose orbit tilts 17 degrees to the ecliptic (Fig. 94), mightFigure 94 The orbits of the planets.Saturn Mercury Venus Earth MarsSunJupiterUranus Neptune Pluto128
