Physics
Scientific paper
Apr 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aps..aprj16001r&link_type=abstract
American Physical Society, April Meeting, April 29-May 2, 2000 Long Beach, CA, abstract #J16.001
Physics
Scientific paper
Likely formation of the solar system in a denser stellar environment increases a chance of a close encounter with a star. In this paper, the results are presented for simulations of stellar passage through an initially thin protoplanetary disk of planetesimals, and a new mechanism of the populating of the Oort cloud is suggested. The calculations show that an encounter with the solar mass star can produce eccentricities and inclinations comparable with those of Kuiper-belt objects even if a distance of the closest approach is a few times larger than the disk radius. Disk-grazing or disk penetrating encounters eject planetesimals from the vicinity of stellar trajectory, and send planetesimals from wider region onto bound but highly eccentric (nearly parabolic) orbits. These orbits can further be circularized with the increasing semimajor axii by tides of distant stars and the planetesimals join the cometary Oort cloud. According to the popular Oort's hypothesis, long period comets were formed closer to the Sun and exposed to higher temperatures and pressures of the solar nebula than short period ones accumulated beyond the planetary system. However, if Oort cloud objects were formed as planetesimals scattered by a passing star, they could be accumulated far beyond the Kuiper belt. The long period comets of this origin would carry isotopic traces of heavy exposure by the Galactic cosmic rays, and contain lower temperature condensates, minerals and organic materials which are unstable or unlikely to form in a planetary region of the solar nebula. Higher D/H ratio in long period comets, like Hale-Boop, is in compliance with the origin beyond the planetary system.
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