From Jupiter-family comets to objects in Encke-like orbits

Abstract

AbstractNumerical integrations of the orbital evolution of objects in orbits resembling the peculiar cometary orbit of 2P/Encke have allowed the identification of the dynamical paths connecting these orbits to the possible source regions and to the possible end states. A certain degree of concentration of the longitudes of perihelion of objects in Encke-like orbits has led to the idea that 2P/Encke and the asteroidal objects in nearby orbits all come from the recent fragmentation of a giant progenitor. However, the fact that the majority of Earth-crossing asteroids are discovered when passing near the Earth induces a correlation between the date of discovery and a range of possible longitudes of perihelion. By combining this correlation with the variable rate of asteroid discoveries over the year, it is possible to show that the discovery of asteroids on orbits of given semimajor axis and eccentricity is favoured if their longitudes of perihelion fall within certain intervals. A question still open is the efficiency of the dynamical path linking the Jupiter family to Encke-like orbits; nongravitational forces seem to play an important rôle in this respect.