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For many astronomers and physicist black holes have been a major focus and an enigma to the common person. Through decades of research, scientists have been able to understand the basic life-cycle of a black hole – in ways thought to be unimaginable, since it was first proposed. But, there are still many misconceptions about what it is. From Science-Fiction movies, many people believe them to be a ‘hole’ in space. Resembling a vacuum, constantly shallowing up the matter that gets too near, and is some sort of wormhole to another dimension. So, for one to understand what it is and what it does, one must understand the creations of how it forms.
Although the term “black hole” was first presented in 1971 by John Archibald Wheeler, it was Pierre-Simon Laplace who first presented the idea of a black hole in 1795. (Hendey) Laplace was a French scientist in the 1800’s, who is well-known for his nebular hypothesis, Exposition Du Systeme Du Monde. He theorized that solar systems were formed by rotating clouds of radiant gas, or in order words black holes. Hypothesizing, that at the center of every solar system there is a black hole, where everything orbits it. Scientist ridiculed and overlook his work because it was seen un-probable at the time. Years later, Albert Einstein published his theory of general relativity in 1915; in which he established that massive entities can cause a distortion in space-time. A year after Einstein’s publication, a German astronomer, Karl Schwarzschild used his theory to define the term black hole. It was not until 1938 when theoretical physicist, Robert Oppenheimer, and his student, Hartland Snyder, considered the possibility that massive stars could collapse and become a black hole.
After being proven they exist, a British physicist, Stephen Hawking, was able to develop a theory that black holes were not entirely black. The term black hole is somewhat misleading because it sounds like, light can be seen from inside the hole. Which is not entirely true. Hawking used the quantum theory – which explains the behavior of the universe at a molecular, atomic, and subatomic level – to a theory that black holes were not entirely black. (Siegal) He noticed that black holes comply with the second law of thermodynamics, and they slightly glow with radiation. This is called Hawking radiation and was published in 1975. Proving that black holes slowly release their mass from the radiation being released. It would take billions of years for a black hole to completely radiate away. Today, black holes are a normally acknowledged theory that even the normal individual has some knowledge of what it is, but there are still many misconceptions that arise to the common person.
Black holes are defined as a dense sphere that’s gravitational field is so strong, not even light can escape. There are three different types of black holes: supermassive, stellar, and intermediate black holes. (Wild) Supermassive black holes are three million times more massive than our sun; possibly existing at the center of every galaxy, constantly growing because of its surroundings. However, their formation is unknown, but scientist theorized they might be a consequence of a developing galaxy. While a stellar black hole can only form when a star, with a mass 20 times greater than our sun, collapses on itself. An intermediate black hole is the most unique out of the three because scientists have not been able to find one. Scientists have only found black holes with a solar mass of 100 and lower, or 10,000 and higher. Never a mass in between, until now.
Scientists have found it impossible to locate one since they could only have formed after the big bang. John Wernz, a freelance science and technology writer, discusses the finding of an intermediate black hole made by the Harvard-Smithsonian Center for Astrophysics. Scientist found a black hole in one of the densest star clusters, 47 Tucanae, with a solar mass of 2,200. Due to the location, scientists predict that intermediate-mass black holes can form in a dense cluster, but it can result in the merging and creating an even bigger black hole. (Wenz)
In addition to the different types, there are two categories each black hole falls into; rotating or non-rotating. Those that rotate are called Kerr black holes, and non-rotating are called Schwarzschild black holes. (Freudenrich) A Kerr black hole is expected to drag space and time alongside it and is the most common form. While Schwarzschild black holes are one of the simplest black holes in space because it only consists of a singularity and an event horizon. Whereas a Kerr black hole also has an ergosphere and a static limit – the boundary that separates normal space and the ergosphere.
Black holes have characterized regions, as briefly discussed before, and is not just a “hole” in space. There are three main regions that make up a black hole: the singularity (the core), the inner event horizon (the opening of the hole), the outer event horizon (the ergosphere), and only Kerr black holes have a static limit. (Freudenrich) The Singularity is the center point of a black hole and is the place where gravity is the strongest. The event horizon can be compared with or called ‘the mouth’ of the black hole. It is the opening of the hole and once something passes through it, it is sucked in and gone for good. The ergosphere, which is located around the event horizon, is the region of distorted space. Theoretically, if an object were to pass through it, the object could be ejected by gaining momentum from the hole’s rotation and can escape with even more energy. Nonetheless, ergosphere should not be confused with the actual hole because it’s the distorted space around it.
To better understand these properties, we must understand the basic principles of gravity. Gravity plays an important role in the life of a black hole. Imagine throwing a rock up in the air, the rock will rise to a point when gravity pulls it back down. (Overbye) Now, let us assume the rock was thrown with enough force and speed, it escapes Earth atmosphere. The speed in which the rock leaves the gravitational pull of Earth is called the escape velocity. Every planet, comet, star, and black hole differ from their mass, the more mass the higher the escape velocity must be. Since a black hole’s mass is compressed into a small radius and is an enormous amount, its escape velocity must be greater the speed of light. Meaning it’s impossible for anything to escape its gravitational pull since nothing is faster than the speed of light. All black holes consist of same three properties: its mass, electric charge, and rate of rotation. (Overbye) To understand how these properties are determined, we must recognize its previous life as a star., and how that star formed.
Stars are self-radiant celestial bodies, consisting of gas, held together by its own gravity, and are born from cold clouds of gas called nebulas. As a nebula forms, over time the core becomes dense enough to create a proto-star. (Mobasher, 115) As the proto-stars mass continues to grow its core temperature increases until nuclear fusion is reached; once it’s reached, a star is born. As time passes the star will start to run out of hydrogen, a critical component in nuclear fusion that keeps it alive. After it runs out, depending on the mass of the star, it will either end up a white dwarf or a neutron star. (Mobasher, 124) But, if the star is massive enough, a neutron star will continue to collapse and form a black hole.
A white dwarf is a ball of matter that is extremely hot and exceptionally dense. They can have a temperature of more than one hundred thousand kelvin, and are slightly greater, in size, than our planet Earth. Yet, they are half as massive as the sun, and over time the white dwarf slowly cools off, forming a black dwarf; no longer produces heat or light, until it dies out. If the star has a mass five times as large than our sun, it will continue the process of nuclear fusion. When it collapses on itself, it becomes denser than a white dwarf, forming into a neutron star. (Mobasher, 129) A massive star, before becoming a neutron star, can become a black hole instead. When a star implodes causing a supernova blast, one of the largest explosion that occurs in space – and if the star is massive enough to collapse to a size within its Schwarzschild radius, it forms a black hole. When it forms a black hole, the star only stops collapsing when the surface of the star approaches the event horizon. Where light cannot get away from the gravitational force. When the surface passes the event horizon, the star stays a frozen collapsing object and is how a black hole’s form.
The theory of black holes existing has been an enigma to the world for a long time. It was not until very recently that scientist have been able to prove they exist and show how they work. However, since we cannot recreate – or closely observed one because the nearest one is 10,000 light years away – a black hole, all the information we have on them are theoretical. Since we cannot closely observer one scientist can only theorize it as a celestial body – whose surface gravity is strong to the point that nothing, including light, can escape from it. Nevertheless, the essential life cycle of a black hole is currently understood in ways thought to be improbable just twenty years prior.

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