A Motivating Exploration on Lunar Craters and Low-Energy Dynamics in the Earth -- Moon System

It is known that most of the craters on the surface of the Moon were created by the collision of minor bodies of the Solar System. Main Belt Asteroids, which can approach the terrestrial planets as a consequence of different types of resonance, are actually the main responsible for this phenomenon. Our aim is to investigate the impact distributions on the lunar surface that low-energy dynamics can provide. As a first approximation, we exploit the hyberbolic invariant manifolds associated with the central invariant manifold around the equilibrium point L_2 of the Earth - Moon system within the framework of the Circular Restricted Three - Body Problem. Taking transit trajectories at several energy levels, we look for orbits intersecting the surface of the Moon and we attempt to define a relationship between longitude and latitude of arrival and lunar craters density. Then, we add the gravitational effect of the Sun by considering the Bicircular Restricted Four - Body Problem. As further exploration, we assume an uniform density of impact on the lunar surface, looking for the regions in the Earth - Moon neighbourhood these colliding trajectories have to come from. It turns out that low-energy ejecta originated from high-energy impacts are also responsible of the phenomenon we are considering.Comment: The paper is being published in Celestial Mechanics and Dynamical Astronomy, vol. 107 (2010

Polytropes - Applications in Astrophysics and Related Fields

This book provides the most complete academic treatment on the application of polytropes ever published. It is primarily intended for students and scientists working in Astrophysics and related fields. It provides a full overview of past and present research results and is an indispensible guide for everybody wanting to apply polytropes

Instability of Embedded Polytropes

The equivalende of two stability criteria (decreasing pressure with increasing radius versus increasing central density with increasing mass) is shown analytically for spherical polytropes without background medium, and numerically for embedded ones. Previous results concerning the instability under external pressure of incomplete (truncated) polytropes within a uniform background medium are shown to be not true. The spherical incomplete embedded polytrope is stable/unstable for the same polytropic indices and for the same background densities as the corresponding compete embedded polytrope