Asteroidal jet streams

Detailed studies of the asteroidal belt are of importance for clarifying whether the asteroids are fragments of an exploded planet or represent an intermediate state in the accretion of planets.A study of the Hirayama family Flora shows that it contains three groups of bodies travelling in almost identical orbits, thus constituting three jet streams.It is shown that the formation of jet streams is difficult to reconcile with the exploded planet view.In order to decide whether the formation of jet streams is a general phenomenon in the asteroidal belt, it is necessary to determine the orbits of a large number of small asteroids.