Astronomy and Astrophysics – Astronomy
Scientific paper
May 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008dda....39.0403b&link_type=abstract
American Astronomical Society, DDA meeting #39, #4.03
Astronomy and Astrophysics
Astronomy
Scientific paper
During a previous study models of the inner Oort cloud were built which included the effect of an embedded star cluster on cometary orbits about the Sun. The main conclusions were: the formation efficiency is about 10\%; the median distance of the cloud to the Sun only depends on the mean density the Sun encountered. We report on simulations which followed the dynamical evolution of these clouds in the current Galactic environment once the Sun left the star cluster. The question is whether or not the dynamical influence of passing stars and the Galactic tidal field is sufficient to replenish the current outer cloud (semi-major axis a ≈ AU) with enough material from the inner cloud (a ≈ AU). Since visible new comets come directly from the outer cloud, a mass estimate only exists for the latter, with a lower limit of 1 Me. The expansion of the inner cloud can yield an estimate of the mass of said inner cloud. Results indicate typically 10% of the comets from the inner cloud land in the outer cloud and are bound after 4.5 Gyr. If one assumes in the extreme case the majority of material in the current outer cloud came from the inner cloud, then a typical value of the mass of the inner cloud is about 10 Me. Since 10% of comets from the Jupiter-Saturn region were implanted in the inner Oort cloud, this implies about 100 Me for the mass of solids in the primordial Jupiter-Saturn region. This extreme case might be remedied as follows: either the effect of GMCs on the inner Oort cloud is much more severe than originally thought, or a two-stage formation process for the Oort cloud, in which the outer cloud was largely populated by comets once the Sun had left its primordial birth cluster.
Brasser Ramon
Duncan Martin J.
Levison Harold F.
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