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Stellar Black Holes
Accretion Disk Around Black Hole. Credit:CXC/M.Weiss
Caption
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When a star runs out of nuclear fuel, it will collapse. If the core, or central
region, of the star has a mass that is greater than three Suns, no known nuclear
forces can prevent the core from forming a deep gravitational warp in space
called a black hole.
A black hole does not have a surface in the usual sense of the word. There is
simply a region, or boundary, in space around a black hole beyond which we cannot
see. This boundary is called the event
horizon.
Anything that passes beyond the event horizon is doomed to be crushed as it
descends ever deeper into the gravitational well of the black hole. No visible light,
nor X-rays, nor any other form
of electromagnetic radiation, nor any particle, no matter how
energetic, can escape. The radius of the event horizon (proportional to the mass)
is very small, only 30 kilometers for a non-spinning black hole with the mass of 10 Suns.
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