If a "white hole" has gravity like that of a black hole, then anything
emitted from inside its event horizon would need to be moving faster
than the speed of light as it crosses that horizon in order to escape
ballistically. Alternativey, it could be emitted by some repulsive force
which causes it to accelerate as it rises.

If the gravity of a white hole is like that of a black hole, and the stuff
being emitted from it is any kind of matter or radiation we know of, and
there is no magical repulsive force causing the stuff to accelerate, then
the stuff will slow down as it leaves, and will get closer together, not
farther apart. Same for black holes as for white. Light from particles
which emerged from the hole earlier would appear blueshifted, not
redshifted, to a particle which emerged later.

I can try to clarify something about Hawking radiation:

Hawking radiation is caused by a combination of two things:

1) Pairs of virtual particles are constantly being created and destroyed
everywhere. They are mostly virtual photons, but include particles of
all kinds. The length of time they can exist normally depends on their
energy, and is described mathematically by the principle of uncertainty.

2) The black hole's extreme gravitational gradient. The gradient causes
some pairs of virtual particles to split up after they form and before they
can be destroyed. One particle goes into the black hole, and the other
escapes. This can only happen very close to the event horizon. A pair
of virtual particles which forms inside the event horizon will both remain
inside the black hole, and nothing special happens. A pair of virtual
particles which forms far outside the event horizon will both escape,
and again nothing special will happen. If one particle falls in while the
other escapes permanently, some of the black hole's mass-energy will
be carried away by the escaping particle. The strength of the gravity
gradient determines how frequently this happens. It happens far, far
more frequently with small black holes than large ones, so small black
holes would have high temperature and evaporate rapidly, while large
black holes would have very low temperature and evaporate very, very
slowly.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves