Tales Behind Black Holes
What are Black Holes?
Black holes are stars that compress themselves at the end of their life to a single point. This point, called the singularity, contains a immense gravitational force around it. This force-field acts like a vaccuum for those objects that come near it. Those objects are able to go into a black hole, but they are not capable of coming out due to the immense gravity surrounding them.
How are they formed?
Black holes are formed from collapse stars. This is because at the end of a star's life, the star burns up the rest of its fuel, thus stops forming heat and stops expanding from the heat. Since there was initially a heat expansion and gravity contraction during a star's life, the gravity contraction becomes greater than the heat expansion, resulting in the star collapsing ("Black" 1). Here is a picture of a black hole from the Hubble Space Telescope.
Theories on Black Holes
In the beginning, scientists based their theories of astronomical phenomenon on Isaac Newton's laws of motion. One theory that was popular in the 18th century, was one by the Reverend John Michell. He stated, in a paper he wrote, the first theoretical formation of a black hole. According to Mitchell Begelman's book Gravity's Fatal Attraction : Black Holes in the Universe , Michell wrote, "If the semi-diameter of a sphere of the same density as the Sun were to exceed that of the Sun in the proportion of five hundred to one, and supposing light to be attracted by the same force in proportion to its vis inertiae [inertial mass] with other bodies, all light emitted from such a body would be made to return towards it, by its own proper gravity" (3). It wasn't until two hundred years later that people found that what Michell was describing was the formation of black holes.
It wasn't until the 20th century when Einstein formed his theory of relativity that scientists got the right idea on how black holes could exist. Apart from the fact that this theory proved that light travels in packet of energy called photons, it also states an idea called general relativity. "Einstein postulated that gravitational fields are manifestations of the curvature of space itself" (Begelman 5). This theory helped many people see that a black hole could exist within the curvature of space. And since the formation of the theory of relativity, many scientists have developed theories that have so far precisely predicted how certain black holes form. One such theory is the idea of the Schwarzchild black hole, formed by Karl Schwarzchild in 1916. His theory was "the first theoretical description of a black hole within the framework of general relativity" by which its said that a person would be able to measure the same radius for the curvature of space if he was
standing in the middle of a black hole (Begelman 8). This one along with the theory of general relativity allowed astrophysicists of the 20th century devise new descriptions of black holes, such as whether the black hole is circular or elliptical, the size of it, etc..
Types of black holes
There are several different types of black holes:
- Schwarzchild black hole- This is a black hole with a neutral charge. This kind of black hole also does not spin. It has one event horizon and one singularity.
- Kerr black hole- This type of black hole spins. A Kerr Black Hole also contains a magnetic field, and because of it, conducts electricity, like a battery It does this through a process called unipolar induction (Begelmann 155).
Are there any known black holes?
So far, scientists have not found an actual black holes, but they have found stars that have properties of becoming a potential black hole. One such star is Cygnus X-1. Scientists used an X-ray satellite to pinpoint the intense X-rays they were receiving from the constellation Cygnus. They have concluded that "Cygnus X-1 may prove to be the first identified black hole" ("Black" 1).