Publication date: May 1976
The motion of particles falling radially from rest at infinity with zero
total angular momentum on to a rotating (Kerr) black hole is studied.
The shell of such particles, initially spherical, becomes prolate along
the axis of symmetry during the fall onto a rotating hole. The shape of
the shell from the viewpoint of distant observers is studied by means of
the photons moving along the (non-shearing) geodesics of the outgoing
principal null congruence. The approach of the particles towards the
horizon in terms of the arrival times of these photons to a distant
observer, the redshift of the radiation and its intensity show
dependence exponentially on the observer’s proper time as in the
non-rotating case, however the characteristic e-folding times become
infinite as the hole’s angular momentum approaches the extreme value. In
the case of an extreme Kerr black hole these exponential laws go over
into power laws.
Bicak, J.; Stuchlik, Z.;