Conférence - David Nesvorný : Following Comets to Their Distant Source Reservoirs and Back
Description
Alessandro Morbidelli
Chaire Chaire Formation planétaire : de la Terre aux exoplanètes
Collège de France
Année 2025-2026
David Nesvorný
Conférence - David Nesvorný : Following Comets to Their Distant Source Reservoirs and Back
David Nesvorný
Southwest Research Institute, USA
Résumé
Comets are icy bodies that originate in the trans-Neptunian region and evolve into the inner Solar System, where they become active due to the sublimation of water ice triggered by solar heating. We describe dynamical models that trace the implantation of comets into their distant source reservoirs during the early Solar System, approximately 4.6 billion years ago. These models are used to predict the present-day orbital distribution and number of active comets, which are then compared to observational data. The results indicate that the scattered disk and the Oort cloud are the primary source reservoirs for ecliptic comets (short-period) and isotropic comets (long-period and Halley-type), respectively. The observed orbital distribution of ecliptic comets is well reproduced if their physical lifetimes are limited to a few hundred perihelion passages within 2.5 astronomical units of the Sun. In contrast, small Oort-cloud comets tend to be more active and typically disintegrate after only a few such passages. Halley-type comets appear to represent an extension of the population of large, returning Oort-cloud comets to shorter orbital periods. We explore how the dynamical structure of cometary reservoirs is affected by the Galactic tide and Sun's birth environment within a stellar cluster.
United States
