In 1916, the German astronomer Karl Schwarzchild attempted to theorize how a star could shrink to become what he called a "Black Hole". Schwarzchild predicted that our sun would have to shrink to less than two miles in radius. He also predicted that even though the sun had shrunk its mass and weight would remain the same, which means that the planets would continue on their orbits, uneffected. Schwarzchild still questioned if stars could become this compact.
In 1934 W. Baade and F. Zwicky predicted that the collapse of a star, strips the atoms of their electrons, thus making it a Neutron Star. He also predicted that these are only 10-15 miles in diameter with a density of about a billion tons per cubic inch.
The American physicists R. Oppenheimer and H. Snyder, in 1939, realized that Schwarzchild theory was only possible if the star was much bigger than our sun; approximately 3.9 times or larger.
In the early seventies, a x-ray source was located in the Constellation Cygnus. The x-ray source couldn't actually be precisely located but was narrowed down to a relatively small area. At this time it was very puzzling for the scientist.
Steven Hawking, in the seventies, came up with theoretical arguments demonstrating that Black Holes aren't entirely black and that it is possible for them to evaporate because they emit radiation. The radiation from a black hole comes from the mass of it, hence the black hole insinuatingly shrinks. While the radiation tediously increases, the mass slowly decreases. So as the radiation from the black hole increases the black hole shrinks and evidently vanishes.
In 1972, scientist pinpointed a radio emission in the same area. This is still puzzling to scientist today but all they knew was that it was originated from the same area as the x-ray source and apparently came from open space. The scientist watched this area for months and finally waited until the spot in space came over the star next to it. When it did there was startling results. The spot in space eclipsed the star next to it. The spot was then named Cygnus X-1 and was officially the first Black hole discovered.
Even back in Isaac Newton's time, scientist speculated such an object existed. So many questions had been answered by the discovery of this mysterious object, yet so many more generated.
A Black Hole is an object that is so dense not even light can escape its gravity. Sense nothing is faster than light, nothing can escape. A Black Hole is the evolutionary endpoint for massive stars at least 10-15 times bigger than our sun. If a star that big undergoes a supernova explosion, it may leave behind a burned-out, massive, super-dense remnant.
With no fuel to have the outward force the remaining star might collapse on its own gravitational force. The star eventually reduces to point zero volume and infinite density, creating a singularity. As the density reaches infinite, photons bend around the singularity and light emitted by the star is bent and is kept within a certain point called the event horizon by the intense gravitational field. Nothing will ever leave the event horizon of a black hole and because no light will ever leave the event horizon, it is referred to as a Black hole.
Contrary to popular belief, a Black hole isn't a cosmic vacuum that consumes everything. For example, if our sun were to become a Black hole the only thing that would change on Earth would be the temperature. The Earth would not be "sucked in". Only matter that entered the event horizon would be "sucked in".
Material that does enter the event horizon is pulled into a spiral. For example if there is a binary stars and one of them turns to a black hole and starts to feed off the brother star, the gas would be pulled into a spiral called the accretion disk. As material gets closer to the Black hole, it heats up and emits X-rays. The closer the material gets to the Black hole the more X-rays it produces.
According to Einstein, a Black hole is where time and space is warped and are different from the outside of the event horizon. So if a observer were watching a person fall into a Black hole from a safe distance, they would see the person fall normally until they entered the event horizon. Then the person would slow down and if the observer could stay alive for a few billion years they would see the person disappear into the singularity at the same moment the Black hole evaporates.
Even today, information about Black holes continue to amaze scientist. Images from the Chandra X-ray Observatory have capture, for the first time, two super-massive black holes circling each other. The black holes will whirl around each other for approximately 100 million years, until they merge.
The two black holes are about the same size as the one in the center of our galaxy and is about the mass of 100 million of our suns. The black holes supposedly are the remains of two separate galaxies that merged 100 million years ago to make the NGC6240 Galaxy. When the galaxies blended they left one extremely bright galaxy with two black holes circling each other on a collision course.
Scientist believe that in about four billion years, the billions of stars in the Milky Way and the Andromeda Galaxies will merge and a similar situation will happen with the two super-massive black holes of our galaxies.
Astronomers say that the two black holes of the NGC6240 galaxy are about 3,000 light-years apart and are traveling at about 22,000 mph. As the black holes grow closer and closer their speed will increase and nearly reach the speed of light before merging, about 671 million mph.
When the black holes merge, their momentum will be converted to gravitational waves and the black holes will spew radiation throughout the universe. Since momentum can't be stopped, the gravitational waves will travel infinite distances thus shifting the gravitational constant throughout the universe.
