Explosive ejections generated by gravitational interactions
  During the fragmentation and collapse of a molecular cloud, it is expected to
have close encounters between (proto)stellar objects that can lead to the
ejection of a fraction of them as runaway objects. However, the duration and
the consequences of such encounters perhaps are small such that there is no
direct evidence of their occurrence. As a first approximation, in this work, we
analytically analyze the interaction of a massive object that moves at high
velocity into a cluster of negligible mass particles with an initial number
density distribution $\propto R^{-\alpha}$. We have found that the runaway
conditions of the distribution after the encounter are related to the mass and
the velocity of the star and the impact parameter of each particle to the
stellar object. Then, the cluster particles are gravitationally accelerated by
the external approaching star, destroying the cluster and the dispersion and
velocities of the particles have explosive characteristics. We compare this
analytical model with several numerical simulations and finally, we applied our
results to the Orion Fingers in the Orion BN/KL region, which show an explosive
outflow that could be triggered by the gravitational interaction of several
(proto)stellar objects.
