Astronomers have had a long-term fascination with the phenomenon of the black hole. Until the later part of the twentieth century, however, they provided little more than inspiration for science fiction writers. As humans, we have traditionally been skeptical of anything we cannot tangibly see or hear or manipulate on some level with our senses. Black holes do not satisfy the criteria for our need of proof. They cannot be photographed, or for that matter seen as they absorb all light. Also, little more has been expected to be gained from exploring black holes than an extrapolation of Einstein's Theory of Relativity. In the past five years however, great strides have been made not only in the realm of empirical proof but in applying the knowledge of black holes to pertinent questions for all of humankind. Black holes may indeed explain the origins of all nature (Kluger, 44). Let's look at black holes in terms of the most prevalent theories at our disposal. First, we will define what we have come to understand as a black hole. We will then touch upon how black holes are documented and measured. Thirdly, we will examine the black hole believed to be at the center of our own Milky Way galaxy. Finally, we will explore the prevalent hypothesis that black holes are in fact the genesis of all galaxies.
What is a black hole?
Gravity is the cause of black holes. A black hole is the unlimited and irresistible force of ultimate gravity in the universe. To understand how a black hole is created, it is helpful to understand a bit about the basics of gravity. Imagine shooting an arrow into the sky. The harder you shoot the arrow, the farther it will go in attempting to escape the pull of the Earth's gravity. If you were to use a big enough bow with enough force you could help the arrow reach speeds exceeding 7 miles per second which is the escape velocity for the Earth. Escape velocity indicates the minimum speed necessary to beat the pull of the planet's gravitational core (Cowen, 390). The strength of the gravitational pull of the core is determined by the density and mass of the core. The denser and more massive that the core is, the greater the gravitational pull. If you were to drop a ball to the center of the earth, the gravitational forces would crush it into an ever shrinking volume requiring even greater amounts of force to help it reach escape velocity. As the greatest theoretical speed for any physical object in the universe is that of light (which travels at 186 thousand miles per second) a mass large and dense enough can actually exert so much force that not even light can achieve escape velocity. The object that can pull even light into it and keep it from escaping is a black hole.
Black holes are powerful anomalies which gravitationally suck all matter within their range into their abyss at such a speed as can only recently be measured. Some astro-physicists believe that a black hole is the product of a supernova violently exploding. "Small stars cool off and glow like cinders for eons, but stars with masses ten times that of our sun explode violently as supernovae, leaving behind a neutron star. They also can leave a black hole. Neutron star remnants of supernova explosions, such as the Crab Nebula and its central star, have been directly observed. However, no such direct evidence had been found of a supernova leaving behind a black hole. Some scientists believe that a supernova is not even required to generate a black hole; a star may just contract gravitationally into one (Hellemans, "Smoking Gun," 34)." Indeed more evidence is being discovered every month that supports this theory of how a black hole is born.
Isaac Newton, father of gravitational and physics, developed the laws that are now used to discover the black holes (Melia, 346). Gravity has a mathematical reality and is the same force that not only keeps us planted on the surface of the earth, but keeps the planets revolving around the sun, and our solar system revolving around the center of the galaxy. Gravity pulls from every direction inward towards the center, like a spherical magnet without a negative pole. The closer an object that has any mass at all gets to the black hole, the harder it is for it to escape. X-rays and lightrays have mass and, if the gravitational pull is strong enough, they cannot escape from a collapsed star. Therefore, our eyes which detect only reflected light, cannot possibly perceive a black hole.
By definition, black holes can't be seen. Theory tells us that deep inside black holes that everything that we know about the universe will come to an end. The mathematics seem unequivocal, when a massive star dies, it will have no choice but to form a black hole. In 1989, a Japanese satellite, Ginga, containing an x-ray receptor, discovered that a small and dim star was rapidly circling about an unseeable object (Sawyer, A12). The radiations of x-rays from that body indicated that it was traveling about the center at enormous speeds. When stars circle about an unseen object, their movement and behavior indicate a black hole.
In 1999, scientists using the Keck Telescope in Hawaii were able to identify by-products of a supernova explosion being absorbed by a resulting black hole. "From the relative abundances of the various elements, Rebolo's team estimates that the progenitor had a mass of twenty-five to forty suns. Most of the mass of the exploding star was ejected as a huge cloud, and the companion star apparently absorbed a lot of it. This is really the first convincing suggestive evidence that the black hole forms in relationship to the supernova explosion (Hellemans, 34)." Another common theory is that a black hole results when a massive star exhausts its nuclear fuel and implodes. If the core of a star contains more than two solar masses, it's destined to collapse and a black hole is made.
The key characteristic of a black hole is its density and therefore its gravitational pull. A black hole can concentrate the mass of hundreds of suns the size of ours into an area the size of our moon. Black holes will feed incessantly on everything within their gravitational pull and will then lie dormant until a galactic event such as a collision knocks more fuel into their field. Dormant holes are even more difficult to discover and prove because of the lack of surrounding debris. "Considered hypothetical until a few years ago, black holes are the sites of extreme gravitational collapse from which nothing, including light, can escape once it has crossed the critical boundary known as the event horizon. This means a black hole itself is invisible. Active black holes are more easily detected, because they are in the messy process of consuming whatever matter has come close to them. The feeding frenzy generates energies far more efficiently than nuclear processes, heating in-falling gas to millions of degrees and virtually sending up flares to mark the hole's existence (Sawyer, "Young Cosmos was full of Black Holes," A12)."
To find these non-matter black holes, scientists have been using a combination of observational and mathematical factors. The primary method of detection used is the x-ray detector. X-rays, in the majority, are released by matter that has been destroyed under extreme conditions. Black holes, then, are the cause of the production of most of the universe's x-rays. By turning censors to pick up x-ray emissions, particularly brief flickering emissions, it is possible to detect the anomaly we call a black hole.
At the center of every galaxy is a massive black hole which draws…