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population which has remained gravitationally bound [13, 14]. It is also worth noting that
about half of the pulsar population will escape the gravitational potential well of the Galaxy,
ending up in intergalactic space, the remainder being in a large galactic halo.
There has been much speculation on the origin of the high velocities, the three main
possibilities being the disruption of binary systems, an electrodynamic “rocket” effect in the
early life of the pulsars and asymmetry in the supernova explosions. The first two have
great difficulty in explaining the size of the velocities and the most likely origin seems to
lie in the supernova explosion itself. The high momentum asymmetry of the neutron star
after the explosion must be matched by that of either the ejecta or neutrinos. The origin
of the asymmetry is not clear, although both convection and the magnetic field have been
cited as the possible determining agents. It is worth noting that up to now, the magnetic
properties of the neutron stars do not seem to implicate the magnetic field in the production
of the high velocities.
References
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