Black holes

As Humans move forward with technology and mathematical concepts, we come to find a greater understandting about the world around us. Black Holes are considered a recent discovery in the almost age-old study of our universe. Since the beginning of our time here on earth, Man has always expressed fascination and interest in the sky above us and everything beyond. Every day we make new discoverys and findings. It is only recently that our study and understanding of the universe has begun to increase almost exponentially both in pace and possibilities. The concept of black holes has been around in loose theory since the late 1700’s, when the French Mathematician Pierre Simon wrote about black stars that he called “dark bodies.” The more commonly used term these days is black holes- a result of more recent work by the American scientist John Wheeler, among others. About the same time as Einstein’s Theory of General Relativity came out (about 1915), Karl Schwarzchild derived a system that describes the spacetime geometry of empty space surrounding any spherical mass. One of the more remarkable predictions of Schwarzchild’s geometry was that if a mass (M) were compressed inside a critical radius (rs) then its gravity would become so strong that not even light could escape. The Schwarzchild radius (or event horizon) rs of mass M is given in mathematical formula like so: rs=2 G M / c2 where G represents Newton’s gravitational constant, and c being the speed of light. A star is defined as a self-illuminating body. When a star runs out of light, it dies. A dead star may do one of many things after its demise. It may shrink until it is a white dwarf (only a few thousand miles or so across- about the size of the earth), it may shrink until it is smaller than a white dwarf and become a neutron star- about 20 miles across (neutron stars have incredible density, about a million tons per square inch). Or, a dead star may continue to shrink until it is simply a point in space with infinite density. This is a black hole. A star shrinks because gravity tries to pull the particles in the star together to make it collapse. If the star is less than two or three solar masses, it usually means that there is enough expulsion principle repulsion to support the star against the pull of gravity. Stars that have masses greater than 3 times the mass of the sun, on the other hand, will most likely turn into black holes. Within the gravitational force of a body in space, it takes a certain speed of an object propelled outward from that body for it to be able to escape, this is what the term escape velocity refers to, the velocity required to break pass a mass gravitational field. If the escape velocity of a star is greater than the speed of light (approximately 300,000 kilometers per second) then nothing, not even light itself, can escape from the star. The limits of anything within a black hole- the “point of no return,” is called the Event Horizon. Black Holes only suck in everything within this certain distance from its center. Anything outside this horizon would, however, be perfectly safe and could orbit the black hole quite successfully without fear of being sucked in. Aside from the event horizon, the other major feature of a black hole is in the center. It is the point of singularity. Singularity is a point where all the known and understood laws of nature cease to exist. Scientists believe that black holes do strange things to the time and space around them. Outside of a black hole the warping of space causes time itself to slow down. If you were to watch a clock fall in to a black hole, the passing of seconds on that clock would slow down as it fell until it passes the event horizon, where you would essentially see time stop. If, however, a person fell into a black hole, they would not notice any passing of time because literally everything slows down within this area- the person’s breathing, thoughts, perception. The person would fall until they reached the point of singularity- where they would explode because of the density. Gravity is a constant force throughout our universe. All objects in space have gravity. While we tend to think of gravity as being a force that attracts or pulls inwards, the actual implications of gravity are a little different. Gravity directly depends on the mass of a body in space. The effect of gravity on space is that it becomes curved. The stronger the gravity, the stronger the warping of the space surrounding it. Until the mid-nineties, there was no actual proof of black holes. Yet the theories surrounding them were so strong that most scientists did not need physical proof to believe in what their equations and formulas told them. When the first real proof of black holes was uncovered, it was seen more as a validation of long held beliefs than as a groundbreaking new discovery. Although different sources quoted different exact dates, it appears that the first proof came in 1992 when NASA’s Hubbell Space Telescope brought home the fist picture of one. The picture was not actually of a black hole, but rather it was an image of a giant disc of cold gas and dust, which scientists believe fuel a black hole. It seems that with all this information on black holes, we should understand them with clarity. And yet, full comprehension of black holes is still not known to us, as has much other knowledge concerning the vastness of time and space. The possibilities that come with black holes and the relevant theoretical implications are inspiring. They bring us a little closer to understanding the makeup of our universe,

Black Holes

.. lack Holes by 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.

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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 a user in Los Angeles can read a newspaper in New York. Other pieces of equipment used are ‘orbiting observatories’ like the Hubble Telescope, which provided the first conclusive proof of black holes.

Orbiting satellites are also used to detect radio waves usually given off by black holes. The British satellite Ariel V discovered the black hole A0620-00 this way. Black holes may be related to the most exotic space phenomenon, quasi-stellar objects, most commonly called quasars. Quasars shine so brightly that astrophysicists think the light must come from superheated matter falling into a black hole. The leading theory about quasars says they may represent the earliest period of evolution of galaxies.

Quasars, so far, are the most distant objects known, some as far as 10 billion light years away. Black holes are usually found in or near companion star pairs. One of the stars is sometimes a dark star, a star that is hard to see or can’t be seen. Bruce Margon from the University of Washington- Seattle says, ” We are finding that black holes come in a large number of sizes. Nature makes them like 50- and 100-watt light bulbs.” Astronomers are finding that for reason, closer black holes are smaller than the more distant ones. Black holes can be located by studying how they affect their surroundings.

A super-massive black hole has been located at the heart of Galaxy M87. It is between 2.5 and 3.5 billion times the size of our sun. The accretion disk at M87 is rotating at at least 1.2 million miles per hour. Some people think that it might be a cluster of neutron stars, but it would take more than 2 billion stars to get something that big. Anything that big in that small of an area would eventually collapse into a black hole anyway. Superluminal jets, groups of high speed electrons which are flung out of galaxies thought to contain black holes, have been detected coming out of M87. Superluminal jets can travel close to the speed, but the fastest one has ever been found was going 93% of the speed of light. The frontier of the M87 black hole is roughly the same distance that Uranus is from the Sun.

Superluminal jets in the Milky Way indicates a black hole is lurking nearby. Astronomers have located something strange, near Sagittarius A* that is less than 1 million times the size of our sun, in the Milky Way. This object doesn’t give off enough radiation to be a normal black hole. Scientists have devised a model that would explain the lower radiation levels. The object is superheating the gases before they enter.

The heated gases move faster so less energy escapes. The model shows that the object can consume 99.9% of the energy that is given off leaving .1% to escape, which would account for the low energy levels. A black hole smaller than the one in Galaxy M87 has been located near the center of the Andromeda Galaxy, with a mass of only a few million solar masses. Near the center of the galaxy, there are two star clusters, one bright the other faint. The bright cluster may be the nucleus of a dwarf galaxy that Andromeda may have captured. The faint cluster is moving at a speed of over 850,000 miles per hour, which is good evidence of a black hole.

If Andromeda holds a black hole it would mean that there is a black hole 50 times closer than the one in M87. Another black hole was discovered in a galaxy less than 21 million light years from Earth. This black hole has a mass of more than 40 million suns. In Galaxy NGC 6240, almost 300 million light years from Earth, astronomers believe to have found a black hole during observations of two colliding galaxies. The black hole is caught between the two galaxies and is expected to merge with them in the next few hundred million years.

It has a mass 10 to 100 times larger than any black hole ever found. It has the mass of the Milky Way in 1/10,000th the area. It may have been left over from an early universe, or a quasar that has burned itself out. Its finding suggests the presence of a lot of unobserved matter and it may be the first step in explaining dark matter or missing mass. The object itself may be a form of dark matter, which makes up 90% of the mass of the universe. In 1975 an X-ray burst and an optical nova lead to the discovery of a black hole.

The black hole A0620-00 is located in the constellation Monoceros. It is a dark object with a mass exceeding 3 solar masses. It is part of a binary system, a pair of stars that orbit each other, consisting of an orange dwarf and itself. Orange dwarfs are very common, in fact they make up more than 15% of star masses. The star is orbiting the black hole. Astronomers have found that only half of the light comes from the star, the other half comes from the accretion disk circling the black hole. Black holes are much more common than astronomers once thought.

Future research may locate many more exotic phenomenon. Astronomers believe there may be thousands of black holes and other mysteries of space, and they hope to learn more about them in the future. References Cowen, Ron. “Repaired Hubble Finds Giant Black Hole” Science News, 145 (June 4, 1994) p. 356 Croswell, Ken. “The Best Black Hole in the Galaxy” Astronomy, (March, 1992) pp. 30-37 Dye, Lee.

“Evidence of Massive Black Hole Discovered by Astronomers” Los Angeles Times, (January 12, 1995) p. A3+ Flamsteed, Sam. “99.9 Percent Sure” Discover, 16 (January, 1995) p. 32 Kaiser, Jocelyn. “Does the Milky Way Hide its Black Hole?” Science News, 147 (April 15, 1995) p.

230 Majeski, Tom. “Evidence of Second Black Hole Detailed” Knight-Ridder/Tribune News Service, (May 31, 1994) p. 0531K6533 Naeye, Robert. “Faster Than Light?” Discover, 16 (January, 1995) p. 33 Sawyer, Kathy. Monstrous, Dark Stranger Seen in Neighborhood of Galaxy” Washington Post, (April 10, 1991) p.

A2 Sawyer, Kathy. “Scientists Detect 12 Black Holes” Las Vegas Review-Journal+ Sun, (August 2, 1992) p. 21E Shipman, Harry L. Black Holes, Quasars, and the Universe Boston, Houghton Mifflin Company, 1980 Taylor, Ronald A. “Astronomers Spot Massive Mystery” Washington Times, (April 10, 1991) p. A4.

BLACK HOLES

BLACK HOLES
Into the Depths of A Black HoleEveryday we look out upon the night sky, wondering and dreaming of what lies beyond our planet. The universe that we live in is so diverse and unique, and it interests us to learn about all the variance that lies beyond our grasp. Within this marvel of wonders our universe holds a mystery that is very difficult to understand because of the complications that arise when trying to examine and explore the principles of space. That mystery happens to be that of the ever clandestine, black hole.This essay will hopefully give you the knowledge and understanding of the concepts, properties, and processes involved with the space phenomenon of the black hole. It will describe how a black hole isgenerally formed, how it functions, and the effects it has on the universe. In order to understand what exactly a black hole is, we must first take a look at the basis for the cause of a black hole. All black holes are formed from the gravitational collapse of a star, usually having agreat, massive, core. A star is created when huge, gigantic, gas clouds bind together due to attractive forces and form a hot core, combined from all the energy of the two gas clouds. This energy produced is so greatwhen it first collides, that a nuclear reaction occurs and the gases within the star start to burn continuously. The Hydrogen gas is usually the first type of gas consumed in a star and then other gas elements such as Carbon, Oxygen, and Helium are consumed.This chain reaction fuels the star for millions or billions of years depending upon the amount of gases there are. The star manages to avoid collapsing at this point because of the equilibrium achieved by itself. The gravitational pull from the core ofthe star is equal to the gravitational pull of the gases forming a type of orbit, however when this equality is broken the star can go into severaldifferent stages.Usually if the star is small in mass, most of the gases will beconsumed while some of it escapes. This occurs because there is not atremendous gravitational pull upon those gases and therefore the starweakens 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 possiblySupernova, 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 most likely that when the star’s gases are almost consumed those gases will collapse inward, 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.This motion absorbs various matter and spins it within the ring (known asthe Event Horizon) that is formed around the black hole. The matter keeps within the Event Horizon until it has spun into the centre where it isconcentrated within the core adding to the mass. Such spinning black holes are known as Kerr Black Holes. Most black holes orbit around stars due to the fact that they oncewere a star, and this may cause some problems for the neighbouring 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, which sweeps all the matter into the Event Horizon, named forit’s flat horizontal appearance and because this happens to be the placewhere mostly all the action within the black hole occurs. When the star is passed on into the Event Horizon the light that the star endures is bentwithin the current and therefore cannot be seen in space. At this exactpoint in time, high amounts of radiation are given off, that with theproper equipment can be detected and seen as an image of a black hole.Through this technique astronomers now believe that they have found a black hole known as Cygnus X1. This supposed black hole has a huge star orbiting around it, therefore we assume there must be a black hole that it is inorbit with. The first scientists to really take an in depth look at black holes and the collapsing of stars, were a professor, Robert Oppenheimer and hisstudent Hartland Snyder, in the early nineteen hundreds. 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 in it’s clutches. **(1)The name “black hole” was named such, because of the fact that lightcould not escape from the gravitational pull from the core, thus making the black hole impossible for humans to see without using technologicaladvancements for measuring such things like radiation. The second part of the word was named “hole” due to the fact that the actual hole, is whereeverything is absorbed and where the centre core presides. This core isthe main part of the black hole where the mass is concentrated and appears purely black on all readings even through the use of radiationdetection 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 ofvarious radiation fluctuations and other diverse types of readings that could be read from the area in which the black hole is suspected to be in.Several diagrams were made showing how astronomers believe that if somehow you were to survive through the centre of the black hole that there would be enough gravitational force to possible warp you to anotherend in the universe or possibly to another universe. The creative ideas that can be hypothesized from this discovery are endless. Although our universe is filled with much unexplained, glorious,phenomenons, it is our duty to continue exploring them and to continue learning, but in the process we must not take any of it for granted.As you have read, black holes are a major topic within our universe and they contain so much curiosity that they could possibly holdunlimited uses. Black holes are a sensation that astronomers are still very puzzled with. It seems that as we get closer to solving their existence and functions, we just end up with more and more questions.Although these questions just lead us into more and more unanswered problems we seek and find refuge into them, dreaming that maybe one day, one far off distant day, we will understand all the conceptions and we will be able to use the universe to our advantage and go where only our dreams could take us.
Works Cited
Depths of a Black Hole**(1): Parker, Barry. Colliding Galaxies. PG#96

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