Journal Article

Where do long-period comets come from? Moving through the Jupiter–Saturn barrier

Piotr A. Dybczyński and Małgorzata Królikowska

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 1, pages 51-69
Published in print September 2011 | ISSN: 0035-8711
Published online August 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19005.x
Where do long-period comets come from? Moving through the Jupiter–Saturn barrier

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The past and future dynamical evolution of all 64 long-period comets having 1/aori < 1 × 10−4 au−1, qosc > 3.0 au and discovered after 1970 is studied. For this sample of Oort-spike comets we have obtained a new, homogeneous set of osculating orbits, including 15 orbits with detected non-gravitational parameters. The non-gravitational effects for 11 comets have been determined for the first time. This means that more than 50 per cent of all comets with perihelion distances between 3 and 4 au and discovered after 1970 show detectable deviations from purely gravitational motion. Each comet was then replaced with a swarm of 5001 virtual comets representing the observations well. These swarms were propagated numerically back and forth up to a heliocentric distance of 250 au, constituting sets of original and future orbits together with their uncertainties. This allowed us to show that the 1/aori distribution is significantly different in shape as well as in maximum position when non-gravitational orbits are included. Next, we followed the dynamical evolution under Galactic tides for one orbital revolution to the past and future, obtaining orbital elements at the previous and next perihelion passages. We obtained a clear dependence of the last revolution change in perihelion distance on 1/aori, which confirmed theoretical expectations.

Based on these results, we discuss the possibility of discriminating between dynamically new and old comets with the aid of their previous perihelion distances. We have shown that about 50 per cent of all comets investigated have their previous perihelion distance below the 15-au limit. This resulted in classifying 31 comets as dynamically new, 26 as dynamically old and 7 as having unclear status. We showed that this classification seems to be immune to perturbations from all known stars. However, discoveries of new, strong stellar perturbers, while rather improbable, may change the situation.

We also present several examples of cometary motion through the Jupiter–Saturn barrier, some of them with a previous perihelion distance smaller than the observed one. New interpretations of the source pathways of long-period comets are also discussed in the light of the suggestions of Kaib & Quinn.

Keywords: celestial mechanics; comets: general; Oort Cloud

Journal Article.  14897 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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