From: Gina Miller (echoz@hotmail.com)
Date: Wed Apr 28 1999 - 23:29:07 MDT
Black holes are thought to form from stars or other massive objects
if and when they collapse from their own gravity to form an object
whose density is infinite: in other words, a singularity. During most
of a star's lifetime, nuclear fusion in the core generates
electromagnetic radiation, including photons, the particles of light.
This radiation exerts an outward pressure that exactly balances the
inward pull of gravity caused by the star's mass.
As the nuclear fuel is exhausted, the outward forces of radiation
diminish, allowing the gravitation to compress the star inward. The
contraction of the core causes its temperature to rise and allows
remaining nuclear material to be used as fuel. The star is saved from
further collapse -- but only for a while.
Eventually, all possible nuclear fuel is used up and the core
collapses. How far it collapses, into what kind of object, and at
what rate, is determined by the star's final mass and the remaining
outward pressure that the burnt-up nuclear residue (largely
iron) can muster. If the star is sufficiently massive or
compressible, it may collapse to a black hole. If it is less massive
or made of stiffer material, its fate is different: it may become a
white dwarf or a neutron star.
Copyright © 1995, The Board of Trustees of the University of Illinois
And also:
Black holes are formed when a star dies.Usually, the star is very
big, which is at least three times as massive as the sun.All of its
mass is squeezed into a single point. At this point, both time and
space stop. It's really hard for us to imagine a place like that, but
that's how it is in the center of a black hole.
The center of a black hole is called a singularity. Within a distance
of the singularity, the gravitational pull is so strong that nothing,
not even light, can escape. That distance is called the event
horizon. It's like the point of no return.
When people talk about the size of a black hole, they are referring
to the size of the event horizon. The more mass the singularity has,
the larger the event horizon is.
Many people think that nothing can escape the gravity of a black
hole. But if this were true, then the whole universe would be sucked
into the black hole. Stars and planets can circle the black hole if
they are far enough away from the singularity. Only if things get to
close to the singularity they cannot escape.
Black holes are truly black. That makes them extremely hard to
detect. When black holes collide with other objects including other
black holes, it will ring with a unique frequency, known as its
natural mode of vibration. This frequency will tell scientists if
they have really detected a black hole. It will also tell them how
big the black hole is and how fast it's spinning.-Chris Morris
Gina "Nanogirl" Miller
Nanotechnology Industries
Web Page
http://www.nanoindustries.com
E-mail
echoz@hotmail.com
Alternate E-mail
nanogirl@halcyon.com
"The science of nanotechnology, solutions for the future."
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