CAOSP abstracts, Volume: 39, No.: 1, year: 2009

Abstract: The Galactic tide is the dominant outer perturber of the orbits of comets in the Oort cloud. Its strength primarily depends on the density of matter in the local Galactic disc. This parameter has been determined with a relatively large uncertainty. The known original orbits of the dynamically new comets provide a possibility of determining the density of the Galactic matter within a study of dynamical evolution of comets in the outer Oort cloud. We describe a procedure how to determine the dynamical density in this way. Using the known orbital characteristics of new comets and the generally accepted assumption of the directionally uniform outer Oort cloud, we determine its radial structure and evaluate the quality of our structure description by comparing the predicted and observed distributions of the angular elements of new comets in the zone of visibility. The whole procedure is repeated for a range of discrete values of the local Galactic-matter density. The best agreement between the predicted and observed angular-element distributions is expected for the actual value of the density, which can be found in this way. For the adopted model of the outer Oort cloud, we find that there is a quite well recognizable relation between the level of the agreement and the value of the local-Galactic-matter density. A value between ≈ 0.21 to ≈ 0.23 M pc-3 corresponds to the best agreement and, thus, can be regarded as the most probable actual value of the density.

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Last update: February 26, 2009