You've inferred exactly what goes on. As one approaches the event horizon of a black hole, the gravitational redshift (slowing) approaches a factor of infinity. Thus as things start to fall in to form a black hole, the rate at which the last stuff falls in (as viewed from far outside) slows down. It turns out that this slowing is enough to prevent the black hole from ever quite completely forming, as viewed from the outside. However, what forms is so close to a complete black hole as to behave like one for most purposes, with the exception of some issues about abstract information loss.
Mike W.
(published on 04/04/2011)
