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: http://star.arm.ac.uk/annrep/annrep2003/node27.html
Дата изменения: Tue May 18 17:48:07 2004 Дата индексирования: Tue Oct 2 05:00:31 2012 Кодировка: |
Jonathan Horner (University of Oxford), Wyn Evans (University of Cambridge), David Asher and Mark Bailey have presented a new classification scheme to describe the great diversity of outer solar system orbits, particularly the planet-crossing objects called `Centaurs'. Up to now, it has been difficult to understand the behaviour of Centaurs as a group, as many of their orbits are extremely unstable by astronomical standards, close approaches to the major planets leading to large changes of their orbits and perhaps even ejection from the solar system on time-scales of millions to tens of millions of years. Gravitational interactions of Centaurs with planets, especially Jupiter and Saturn, also cause them to migrate into the inner solar system, even onto Earth-crossing orbits.
The new classification scheme, which is primarily designed to describe the diverse orbits of Centaurs, is intended to improve understanding of the dynamical properties of this class of object, many of which eventually evolve onto short-period cometary orbits, perhaps even Earth-crossing orbits. Owing to the large sizes of the known Centaurs, these objects are also occasionally described as `giant comets'. The passage of such an object through the inner solar system would produce a variable amount of interplanetary dust, such `dustings' occurring on time-scales on the order of 100,000 years or so, comparable to the mean interval between impacts of kilometre-size asteroids on the Earth. The accretion of dust and larger meteoroids contained within the cometary dust trail could pose a serious environmental hazard to Earth, possibly affecting the Earth's climate. The work on Centaurs therefore contributes to a better understanding of the long-term Near-Earth Object (NEO) hazard to civilization.