Freedman and Kaufmann
A black hole
is the end result for only the most
massive stars. These stars live fast
and die young, fusing elements all the way
up to iron in their cores, then
producing a tremendous supernova explosion.
After the explosion, if the remaining material
is massive enough, it becomes a black hole.
A black hole has so much mass and such a small
radius that the force of gravity is enormous
(see the Universal Law of Gravitation). In fact,
the mass is so big and radius so small that escape
velocity for the star (now black hole) exceeds
the speed of light. In other words, nothing can
now escape this black hole, not even light, since
the escape velocity is greater than the speed
of light and nothing can go faster than the
speed of light.
Freedman and Kaufmann