On the origin of the planetary spin angular momentum by accretion of planetesimals - Property of collision orbits

The planar-restricted three-body problem is presently used to ascertain the property of the totality of orbits colliding with a protoplanet of nonzero radius, thereby determining that the angular momentum acquired by a protoplanet critically depends on the planetesimals' orbital eccentricities. It is further noted that the spin rate is virtually independent of the protoplanet radius for a given mass, and that it is larger for a larger radius if the numerical results obtained are interpreted three-dimensionally. Angular momentum will be positive if planetesimals flow into the Hill sphere of the protoplanet. 12 refs