Orbital Coupling Between Distributions Of Semimajor Axis And Inclination Of Near-Earth Asteroids Segregated At About 2 AU

摘要

We investigated the cause of somewhat bimodal distribution of the Near-Earth Asteroids (NEAs) inclination. Numerical integrations, in term of Newtonian gravitation including thermal effect, were carried out on 270 artificial objects for 400 thousand years and on a thousand random-selected NEAs for one million years. Orbital coupling between distributions of semi major axis (a) and inclination (i) segregated at about 2 AU turns out to exhibit bump at about inclination of about 20°. This bump is emerged because of the diversity in orbital mobility of NEAs between regions of a < 2 AU and a > 2 AU, in which correspond to the secular and the mean-motion resonances. NEAs which located at a > 2 AU are dominated by the asteroids whose i < 15° and are protected by the secular resonance (υ6) of Saturn. In addition, thermal effect play a role in delivering NEAs through perihelia of the Terrestrial planets, mainly affect orbital diffusion of NEAs when passing through the υ_6 region, and somehow restrain NEAs from falling into the Sun.