Supermassive Black Holes, Research Paper Example

Black holes, due to their destructive capacities and abnormal capability to distort space time, have become a beloved subject for science fiction novelists. Nonetheless, black holes are no fiction. For decades they were acknowledged as the most devastating force in the Universe. These days, owing to the chain of astounding findings, the perception of supermassive black holes has experienced an impressive transformation. Scientists have discovered that these objects may have played a crucial role in the formation of the early universe, generating the formation of stars, planets, or even life itself. “They may have contributed as much as half of all the radiation produced after the Big Bang, and at least 300 million of them may now be lurking through the vast expanses of the observable cosmos. The most accessible among them appears to be lurking at the Center of our own Galaxy.”[1]

Hundreds of black holes are out there all over the Universe. But what are they? The formation, structure and functioning of black holes have now been studied for almost a century. With the evolution of scientific opportunities, astronomers managed to provide numerous surprising and exciting discoveries. To understand the nature of supermassive black holes, it is crucial to first analyze the fundamental essence of the black holes in general, since supermassive black holes are not a separate phenomenon but rather a subtype.

Black holes are extremely compact objects, with ordinary gravity developed to such an extent that it overpowers all other forces in the Universe. In other words, being small and containing huge mass, it is strong enough to prevent anything, including light, from escaping its surface. Once inside, nothing can break away from a black hole’s gravity, not even a single spot of light.

Nobody has yet discovered a black hole for sure. To verify that those spectacularly powerful, compact objects discerned in the sky are the actual black holes, astronomers would have to identify and measure the effects that only a black hole is able to cause. However, how could human beings, with our comparatively limited scientific methods, measure a harsh bending of a light beam or an extreme slowing of time? Therefore, we can now only hypothesize on the nature of black holes, not yet ready to deal with these monsters physically.

Because of lacking possibilities to actually observe them directly, research on black holes has been doomed to linger on for decades, scientists dealing with hypotheses blindly. Albert Einstein’ general theory of relativity first allowed for the assumptions concerning the existence of these fantastic phenomena. However, French scientist Pierre-Simon Laplace (1749-1827) was one of the first who proposed the probable existence of black holes. Basing his 18th century discussions on the already known laws of gravity, he theorized that the objects, smaller in size and yet more massive than others, produce greater gravitational force. He was also the first to assume that if an object was either particularly massive or exceptionally small, it might not be achievable at all to break out of its surface.

In 19^th century the term “black hole” was first introduced by American physicist John Archibald Wheeler. He was also the one who initiated advanced studies of black holes’ nature, and made significant contributions into the discovery of their properties. It has been found out by numerous challenged scientists that space and time in proximity to black holes takes on many extraordinary qualities.

The day finally came when astronomers recovered their sight, – the Hubble Space Telescope was constructed. “Revealing in 1994 that something was orbiting rapidly around the nuclei of some distant galaxies, suggesting the presence of a huge mass contained in a very small area,” it has finally presented the first factual proof of the existence of supermassive black holes. From that moment on, the huge, high-resolution ground telescopes including the Hubble, the Keck, NASA’s orbiting Chandra X-Ray Observatory, and others “have begun to unravel more about these central black holes — which can be as large as the distance from the sun to well past Mars, and as small as New Jersey.”[2]

The astronomers have also discovered that black holes are formed when massive stars die. Jeffrey McClintock describes the black holes’ formation as a process when “a massive star runs out of nuclear fuel and is crushed by its own gravitational force. While a star burns fuel, it creates an outward push that counters the inward pull of gravity. When no fuel remains, the star can no longer support its own weight. As a result, the core of the star collapses. If the mass of the core is three or more solar masses, the core collapses into a singularity in a fraction of a second.”[3]

The outside face of a black hole is identified as the ‘event horizon’. Black holes do not have a normal surface that can be observed or felt. The event horizon is a pretend globe that determines a safe distance from the hole’s center. Once an object has passed it, it is no more possible to break out: “At the event horizon, the pull of gravity becomes infinitely strong. Thus, an object can exist there for only an instant as it plunges inward at the speed of light.”[4] The event zone, its radius in particular, is used by astronomers to identify and measure the size of a black hole. The radius is named the Schwarzschild radius, after the German scientists Karl Schwarzschild (1873-1916) who had initially found out the keys to the equations of general relativity that explained the nature of non-spinning black holes.

“The radius of a black hole measured in kilometers equals three times the number of solar masses of material in the black hole,”[5] while single solar mass equals the actual mass of the sun.

Astronomers have discovered black holes with event horizons varying from 6 miles to the size of our solar system. Theoretically, black holes can subsist with either smaller or bigger horizons. “By comparison, the Schwarzschild radius of the Earth is about the size of a marble. This is how much you would have to compress the Earth to turn it into a black hole.”[6] A black hole does not necessarily have to be huge, but it does have to be extremely compacted.

Scientists have been long intrigued by the question: “What is inside the black hole?” Unfortunately, we cannot take a look at what is going on beneath the event horizon of a black hole because any sort of substance, neither light nor material, could never reach us back once getting there. Even if we were able to organize an expedition into the black hole, the explorer could never communicate back to us.

The gravitational force is strong in the vicinity of a black hole since all the black hole’s substance is clustered at a single small point in its heart. Scientists term this point ‘a singularity’. Astronomers suggest that all the subjects swallowed by a black hole are mounted up in a single mound at the middle, without, however, being able to actually explain how such a central singularity works. If relying on available researches, one may assume it to be much smaller than an atom’s nucleus.

Black holes generally do not look alike, their appearances are dissimilar. Nevertheless, all black holes are perfectly identical in their nature, and look different due to multiplicity in what is going on in their surroundings. There are, however, three characteristics by which black holes are diversified. These are: “the mass of the black hole (how much stuff it is made of), its spin (whether and how fast it rotates around an axis), and its electric charge.”[7] It is curious to know that black holes completely obliterate all the intricate attributes of the objects they capture.

Therefore, black holes are not necessarily static; there are black holes that spin around an axis. Their rotation velocity cannot go above specified limit. Scientists assume that many black holes in the Universe most likely do spin, since the materials by which they are shaped (e.g. stars) usually also rotate. Logically, the nature of their functioning differs from that of black holes that do not spin. Their situation is much more complex in structure. Spinning black holes produce a sort of a whirlpool, dragging around the surrounding space. The center singularity of such objects is represented by an extremely thin ring rather than a single point. “The event horizon is composed of two, instead of one, imaginary spheres. And there is a region called the ergosphere, bounded by the static limit, where you are forced to rotate in the same sense as the black hole although you can still escape.”[8]

Scientists evaluate the mass of black holes by investigating the objects that move around them. Up to now, two types of black holes have been discovered: a stellar-mass, which is a few times larger than the Sun, and supermassive black hole, which is almost as big as a minor galaxy. As recent investigations have implied, black holes may also fall into other mass categories (Micro black hole, Intermediate mass black hole). Generally, they are ranging between stellar-mass and supermassive. The biggest supermassive black hole now discovered is positioned in OJ 287, it has a mass of 18 billion solar masses.

Due to the advanced studies we now know that the Universe is practically crowded with billions of black holes. Most scientists assume that the galaxy in which our solar system is situated, the Milky Way Galaxy, is as well full of black holes. Astronomers have indeed discovered several black holes in the Milky Way, which are mostly contained in binary stars producing X rays. The mere black hole is unseen, but can be discerned due to the materials falling into or being pulled towards it. Detecting such materials through conscientious observations of the sky, astronomers have, therefore, been able to discover and measure the mass of many black holes in the Universe.

For instance, a black hole can magnetize gas from a star and warm it up. If a binary star normally represented by two stars that orbit each other, has a black hole, it is then closely orbited by this compact object, which strips gas from it. As the gas falls fiercely toward the black hole, tension between the gas atoms warms up the gas in the vicinity of the event horizon so that its temperature may reach several million degrees. “The heated gas would give off rays of energy called X rays. Scientists can use special telescopes to see these X rays. If scientists know where the X rays are, they can locate the black hole.”[9]

How do black holes grow to be supermassive anyway? Black holes generally gain mass by swallowing surrounding objects, mostly represented by dust and gas. It is clear now that whatever reaches the event horizon is doomed to be sucked inside by a black hole’s forceful gravity. Therefore, materials that do not keep a secure distance get captured. However, when we deal with supermassive black holes, which are as huge as hundreds of thousands to billions of solar masses, the process is not that clear.

Astronomers have proposed a number of models for the creation of black holes of this size. The most obvious idea suggests that after a single star-like black hole is shaped, by capturing huge amounts of surrounding material for the duration of millions of years, it eventually grows into a giant, – a supermassive black hole. Another option is that a collision of two stellar-mass black holes occurs and those objects eventually come together to produce a sole, supermassive black hole. One more possibility is that a single massive gas cloud crushes to give way to a supermassive black hole.

Supermassive black holes, the biggest black holes in the Universe, are nowadays thought to be positioned in the center of each existing galaxy. Bigger galaxies normally contain larger black holes. The mass of each of those gigantic holes is believed to vary between 1 million and 1 billion solar masses. This assumption was based on the optical and radio observations that showed that the speed of stars or gas clouds traveling around the centers of galaxies experienced a sudden and significant raise. “High orbital velocities mean that something massive is creating a powerful gravitational field which is accelerating the stars. X-ray observations indicate that a large amount of energy is produced in the centers of many galaxies, presumably by the in-fall of matter into a black hole.”[10]

For years, scientists were struggling to find out the nature of puzzling power hidden in the very center of the Milky Way. Finally, several years ago, the research of an UCLA astronomer Andrea Ghez finally gave the key to this problem. Nowadays, we finally have factual data proving that a supermassive black hole exists at the very core of our galaxy. A radio-wave source called Sagittarius A* (SgrA*) in fact has turned out to be a supermassive black hole. The nature of SgrA* was revealed due to an unusually speedy transfer of stars around it. “The fastest of these stars appears to orbit SgrA* every 15.2 years at speeds that reach about 3,100 miles (5,000 kilometers) per second. The star’s motion has led astronomers to conclude that an object several million times as massive as the sun must lie inside the star’s orbit.”[11] Therefore, a mysterious object which managed to fit inside the star’s orbit and be extremely massive at the same time could be nothing else but a black hole.

Surprisingly, the scientists have discovered that the black holes’ size and character are strongly connected to the size and structure of the adjacent galaxies. The close observations of these cosmic monsters revealed that besides being destructive and swallowing everything around, sometimes including even stars, they may also provide answers to the problem of galaxies’ past and current formation. Supermassive black holes have also proved to perform a creating function, by sending out radiation produced through the aggressive feeding process and the super-high-energy jets, “which can be millions of light-years in length, are believed to seed galaxies with the mass and energy that will, in time, become new stars and perhaps even planets.”[12]

The latest researches have also contributed to the understanding of a tremendous power supermassive black holes have. Such is for instance the discovery, suggesting that these massive objects are able “to strip massive galaxies of the cool gases required to form new stars, leaving ageing red giants to splutter out of existence with no stars to replace them.”[13] Referring to the stated relation between the size of the galaxy and that of the black hole it bears in the center, scientists now assume that supermassive black holes tend to grow in proportion to their host galaxies, and eventually destroy them. And even though the massive galaxies are in minority, they seem to be producing more energy than any other object in the Universe.

Naturally, having a supermassive black hole practically on our own doorstep, only about 25000 light years away, does sound somewhat creepy. Nevertheless, the supermassive black hole the Milky Way has, with its mass of approximately four million suns, appears to be latent and undersized, comparing to the larger black holes, reaching the mass of hundreds of millions to many billions times as massive as our sun. It does not as well spew out the jets of radiation the bigger objects do. Therefore, we are perfectly safe as to the destructive power that lurks in our home galaxy.

Black holes, supermassives in particular, are grand, impressing, mysterious and shocking. They have power that can hardly be taken in by the human brain, and are sometimes described as a cosmic virus created by nature. In spite of suggesting numerous theories explaining the formation and nature of this phenomenon, astronomers, however, still fail to reach a consensus on any of those issues. No doubt the investigations and observations being currently performed are about to result into more shocking discoveries, and one can only guess what other mysteries do the black holes, crowding the universe, posses.

Works Cited

“Black Hole: Gravity’s Relentless Pull.” HubbleSite. Black Hole Encyclopedia. 29 Apr. 2010.<http://www.hubblesite.org/explore_astronomy/black_holes/encyclopedia.html>.

Kaufman, Marc. “Huge Black Holes May Hold Keys to Galaxy Formation.” Washington Post.
31 Oct. 2007.

McClintock, Jeffrey E. “Black hole.” World Book Online Reference Center. 2004. 29 Apr. 2010. <http://www.worldbookonline.com/wb/Article?id=ar062594>.

“Supermassive Black Holes.” Chandra X-Ray Observatory. 18 Sept. 2008. 29 Apr. 2010. < http://chandra.harvard.edu/xray_sources/blackholes_sm.html>.

The World Book Student Discovery Encyclopedia. “Black Hole.” Chicago: World Book, Inc., 2005.

University of Nottingham. “Supermassive Black Holes Strip Massive Galaxies of Star-Forming Gases.” ScienceDaily. 16 Apr. 2010. 29 Apr. 2010 <http://www.sciencedaily.com­ /releases/2010/04/100416095800.htm>.

[1] University of Nottingham, “Supermassive Black Holes Strip Massive Galaxies of Star-Forming Gases,” Science Daily 16 Apr. 2010. 29 Apr. 2010 <http://www.sciencedaily.com­ /releases/2010/04/100416095800.htm>.

[2] Marc Kaufman, “Huge Black Holes May Hold Keys to Galaxy Formation,” Washington Post, 31 Oct. 2007.

[3] Jeffrey E. McClintock, “Black hole,” World Book Online Reference Center, 2004. 29 Apr. 2010 <http://www.worldbookonline.com/wb/Article?id=ar062594>.

[4] Jeffrey E. McClintock.

[5] Jeffrey E. McClintock.

[6] “Black Hole: Gravity’s Relentless Pull,” HubbleSite, Black Hole Encyclopedia, 29 Apr. 2010 <http://www.hubblesite.org/explore_astronomy/black_holes/encyclopedia.html>.

[7] “Black Hole: Gravity’s Relentless Pull,” HubbleSite, Black Hole Encyclopedia.

[8] “Black Hole: Gravity’s Relentless Pull,” HubbleSite, Black Hole Encyclopedia.

[9] The World Book Student Discovery Encyclopedia, “Black Hole,” Chicago: World Book, Inc., 2005.

[10] “Supermassive Black Holes,” Chandra X-Ray Observatory 18 Sept. 2008. 29 Apr. 2010 < http://chandra.harvard.edu/xray_sources/blackholes_sm.html>.

[11] Jeffrey E. McClintock.

[12] Marc Kaufman.

[13] University of Nottingham.