Stars

Stars are huge balls of glowing gas in the sky. The closest
star to the earth to look like a ball is the sun. The other
stars are too far away and only look like pinpoints of
light. 

A star consists of two gases -- hydrogen and helium. The
star shines because atomic energy makes these gases very
hot. When it runs out of hydrogen gas, the star may explode
into a huge cloud of gas and dust. Astronomers believe that
most stars have enough hydrogen to last billions of years. 

A star manages to avoid collapsing because of the
equilibrium achieved by itself. The gravitational pull from
the core of the star is equal to the gravitational pull of
the gases, forming a type of orbit. When this equality is
broken, the star can go into several different stages.
 
Usually if the star is small in mass, most of the gases
will be consumed while some of it escapes. This occurs
because there is not a tremendous gravitational pull upon
those gases and therefore the star weakens and becomes
smaller. It is then referred to as a White Dwarf. If the
star was to have a larger mass however, then it may
possibly Supernova, meaning that the nuclear fusion within
the star simply goes out of control causing the star to
explode. After exploding, a fraction of the star is usually
left (if it has not turned into pure gas) and that fraction
of the star is known as a Neutron Star. 

A black hole is one of the last option that a star may
take. If the core of the star is so massive, (approximately
6-8 solar masses; one solar mass being equal to the sun's
mass), then it is probable that when the star's gases are
almost consumed those gases will collapse inward. They
would be forced into the core by the gravitational force
laid upon them.
 
After a black hole is created, the gravitational force
continues to pull in space debris and other type of matters
to help add to the mass of the core, making the hole
stronger and more powerful.
 
Most black holes tend to be in a consistent spinning
motion. The action absorbs various matter and spins it
within the ring (known as the Event Horizon) that is formed
around the black hole. The matter keeps within the Event
Horizon until it has spun into the center where it is
concentrated within the core adding to the mass. Such
spinning black holes are known as Kerr Black Holes.
 
Most black holes orbit around stars which may cause some
problems for the neighboring stars. If a black hole gets
powerful enough it may actually pull a star into it and
disrupt the orbit of many other stars. The black hole could
then grow even stronger (from the star's mass) as to
possibly absorb another.
 
When a black hole absorbs a star, the star is first pulled
into the Ergosphere. From there, it is swept into the Event
Horizon, named for its flat horizontal appearance. This is
the place where all the action within the black hole
occurs. When the star reaches the Event Horizon, its light
is bent within the current and therefore cannot be seen in
space. At this point, high amounts of radiation are given
off, and with the proper equipment it can be detected and
seen as an image of a black hole. 

Using this technique astronomers now believe that they have
found a black hole known as Cygnus X1 which appears to have
a huge star orbiting around it.
 
The first scientists to really take an in depth look at
black holes and the collapsing of stars were Professor
Robert Oppenheimer and his student Hartland Snyder in the
early 1900's. They concluded, on the basis of Einstein's
theory of relativity, that if the speed of light was the
utmost speed over any massive object, then nothing could
escape a black hole once it is in its clutches. (1)
 
The name "black hole" was coined because light could not
escape from the gravitational pull from the core, thus
making the black hole impossible for humans to see it
without using a technical device for measuring such things
like radiation. The second part of the word, "hole", was
used because it is the spot where everything is absorbed
and where the center core presides. This core is the main
part of the black hole where the mass is concentrated and
appears purely black on all readings even when using
radiation detection devices. 

Just recently a major discovery was found with the help of
a device known as The Hubble Telescope. This telescope has
just recently found what many astronomers believe to be a
black hole, after being focused on an star orbiting empty
space. Several picture were sent back to Earth from the
telescope showing many computer enhanced pictures of
various radiation fluctuations and other diverse types of
readings that could be read from the area in which the
black hole is suspected to exist.
 
Several diagrams were made showing how astronomers believe
that if somehow one were to survive within the center of
the black hole, that there would be enough gravitational
force to possible warp you to another end in the universe
or possibly to another universe. The creative ideas that
can be hypothesized from this discovery are endless.
 
Stars appear to have different colors. They differences are
caused by the temperature of their surface. The temperature
varies from about 5,000 degrees F. for red stars, such as
Betelgeuse, to about 50,000 degrees F. for blue stars, such
as Rigel. Stars of other colors have surface temperatures
somewhere in between. The sun, a yellowish star, has a
temperature of about 10,000 degrees F. 

The brightness of a star depends on the amount of light
energy that a star sends out, not on its size or its
closeness to the earth. Rigel is smaller and farther from
the earth than is Betelgeuse, yet Rigel sends out so much
more light energy that it looks brighter than Betelgeuse. 

Astronomers use an instrument called a photometer, attached
to a telescope, to measure the brightness of stars. When
the light from a star enters the photometer, it produces an
electric current in ti. An electrical meter indicates the
star's brightness in terms of the strength of the current. 

References:
 
(1) Parker, Barry. Colliding Galaxies. PG#96