Two-Step Simulation for the Formation of Asteroid Itokawa from the Restricted Three-Body Problem to the Multi-Body Problem

抄録

This paper studies a formation of Asteroid Itokawa in 2-dimension, dividing the formation process into two steps. The first step is a collapse of parent bodies and the second step is the attachment of small fragments to the early Itokawa that is created by the first step. In the first step, the aggregation of fragments after a head-on impact of two parent bodies is investigated by utilizing the N-body problem with the spring-dumper system. The radius of each fragment and the total mass in the system are set to be 32 meters and 10 times as large as Itokawa, respectively. It is found in the first process that the collision of two parent bodies allows a formation of the early Itokawa that is made by a soft contact of two primary bodies. In the second step, 500 fragments are randomly positioned around the early Itokawa and their motions are numerically analyzed by applying the circular restricted three-body problem. It shows that the population of fragments around the early Itokawa is almost constant regardless of the Jacobi integral, the conserved value in the problem. It implies that fragments may play a role in creating the current shape of Itokawa.