Another reservoir for comets?Debris left over from the formation of Uranus and Neptune may have created a comet belt in the outer solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. just as massive as the belt of asteroids This is a list of numbered minor planets, nearly all of them asteroids, in sequential order. As of late September 2007 there are 164,612 numbered minor planets, and many more not yet numbered. Most asteroids are ordinary and not particularly noteworthy. between Mars and Jupiter. The proposed belt would serve as a storehouse of short-period comets, supplementing the larger and more distant Kuiper belt Kuiper belt: see comet; Kuiper, Gerard Peter. Kuiper belt or Edgeworth-Kuiper belt Disk-shaped belt of billions of small icy bodies orbiting the Sun beyond the orbit of Neptune, mostly at distances 30–50 times Earth's distance , a reservoir that lies beyond the orbits of Neptune and Pluto. To date, no one has even looked for residents of a storehouse between the orbits of Uranus and Neptune. However, calculations by Matthew J. Holman Matthew J. Holman (* 1967) is a Smithsonian Astrophysicist and lecturer at Harvard University. Holman studied at MIT, where he received his bachelor's degree in mathematics in 1989 and his PhD in planetary science in 1994. of the University of Toronto's Canadian Institute for Theoretical Astrophysics Makeup CITA has a small number of long-term faculty members, and a larger number of short term (3- or 5-year) postdoctoral positions, as well as an active visitor program; the purpose of the relatively high influx of new researchers or visitors is to ensure that timely topics indicate that a relatively stable, narrow ring of comets could lie 24 to 26 times Earth's distance from the sun. According to Holman's computer simula- tions, about 0.5 percent of the small, icy bodies in this region could have survived there since the birth of the solar system. The belt is leaky, and many of its residents may have been ejected either by the powerful gravitational grav·i·ta·tion n. 1. Physics a. The natural phenomenon of attraction between physical objects with mass or energy. b. The act or process of moving under the influence of this attraction. 2. tug of a planet or a chance collision. Most would have left the solar system, but some could have traveled inward. The belt is a possible source both of centaurs-large cometlike objects found at great dis-tances from Earth-and of comets that visit the terrestrial planets at least once every 200 years. Although Harold F. Levison Harold F. "Hal" Levison is a planetary scientist specializing in planetary dynamics. He argued for a distinction between what are now called dwarf planets and the other eight planets based on their inability to "clear the neighborhood around their orbits," although his proposal of the Southwest Research Institute's office in Boulder, Colo., says he finds Holman's idea intriguing, he's "dubious as to whether this belt could be long-lived." The decided tilt of Uranus, as if something had knocked the planet on its side, and the unusual, retrograde motion of Neptune's moon Triton suggest that these two planets formed during a violent process, which could have destroyed the fragile comet belt. However, if the violent epoch ended quickly or if the belt were replenished soon afterwards, it might have survived. It's important to search for this storehouse, says Holman, because its presence-or absence-may speak volumes about the pro-cess of planet formation. |
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