Black Holes

Table of Contents
I. What are black holes?
II. Where do they come from?
III. Interesting facts about black holes.
IV. How are they discovered?
A. X-ray Emissions
B. Exotic Energy Sources
C. Star speeds
D. Masers
E. The Baseline Array
F. Hubble Telescope
G. Satellites
V. Quasi-Stellar Relations
VI. Locations
A. M87
B. Milky Way
C. Andromeda
D. ??????
E. NGC 6240
F. A0620-00

What are black holes? Black holes are the remains of a massive star that has collapsed and shrunk
to a tiny point in space. They have all of the gravity of the star concentrated into that point. Black holes
are difficult to see because they cannot be seen. They cannot be seen because they are spinning faster than
the speed of light and light cannot escape from them. They can be compared to a giant vacuum cleaner,
they suck in anything that gets near them.
Where do black holes come from? Black holes are formed when giant stars run out of fuel and are
overwhelmed by their own gravity. When this happens they cannot keep from collapsing. After stars
collapse, they start rotating and as they are
spinning, their gravity becomes stronger causing them to shrink. As the object becomes smaller, it starts
spinning faster and faster.
Using a small black marble as an example of the size that Earth would become if it collapsed and
became a black hole, Todd R. Lauer, of the National Optical Astronomy Observatories said, " Black holes
are very messy eaters. If you took that marble to an 'all-you-can-eat buffet' allowing it to consume all the
matter around it, the feeding frenzy would produce as much radiation as the Sun." Research indicates that
black holes may have existed at the beginning of time. Black holes are so dense that not even light can
escape. Looking towards a black hole, the stars behind it would appear out of place because black holes
distort light. The immense gravitational pull of black holes is thought to be responsible for the swirling
masses of stars in spiral galaxies throughout the universe. Gravity in a black hole should be able to pack
stars in so tight that the intensity of the stars' light would drastically increase towards the center of gravity.
Everything falling into a bla!
ck hole loses its identity, you couldn't tell if it were a satellite or a T.V. set that fell in. Dr. Fred Chromey
of Vassar College in New York said, " Black holes are the easiest way to explain some of the strange things
that are going on in some of the galaxies." Research indicates that if a black hole formed, it would
eventually evaporate but it would take millions of years.
Earth's escape velocity, the speed it takes to escape the pull of gravity, is 11 kilometers per second.
The escape velocity of a black hole is 300,000 kilometers per second, which is faster than the speed of
light. If Earth's diameter shrank to less than 1 centimeter, the escape velocity would exceed the sped of
light, the escape velocity of a black hole. Anything can become a black hole if you compress it enough.
How are black holes located? Black holes technically can't be seen, but they give off many clues
to their location. Signs of many black holes have been located during normal observation of other space
objects. Abnormally high levels of X-rays and gamma rays are the most common clues, but other exotic
energy sources are also good clues. Astronomers have also located black holes by studying the speeds of
swirling galaxies. If large objects are moving at very high speeds astronomers usually try to track their
orbits and try to locate a central object that could be the source of the gravity. Another clue to the location
of black holes are masers. Masers are the cosmic relatives of lasers. They are water molecules orbiting
black holes that capture and amplify radiation and send it back out into space. Masers are usually located
in the accretion disk, the swirling cloud of gases above a black hole. Some masers have been clocked
traveling over 650 miles per second.
Many types of equipment are used to locate black holes. One type of equipment is called the
Baseline Array. The Baseline Array consists of 10 radio dishes, each 82 feet across, spaced across a 5,000
mile area. It acts as one 5,000 mile wide telescope. The Baseline Array is so accurate the