vity keeps captured material from escaping. Of course, every moon, planet, and star has gravity. Earth has enough gravity that you have to travel faster than 11 kilometers per second to overcome the force of gravity. This number is Earth’s escape velocity. The gravity of Jupiter is even stronger: it’s escape velocity is 60 kilometers per second. A black hole has so much gravity that to escape one you would have to be traveling faster than the speed of light, 300,000 kilometers per second. But traveling faster than the speed of light is impossible, so once you get into a black hole you can’t get out.(Levitt 83) Black holes may form during the course of stellar evolution. As nuclear fuels are exhausted in the core of a star, the pressure associated with their heat is no longer available to resist contraction of the core to ever higher densities. Two new types of pressure arise at densities a million and a million billion times that of water, respectively, and a compact white dwarf or a neutron star may form. If the core mass exceeds about 1.7 solar masses, however, neither electron nor neuron pressure is sufficient to prevent collapse to a black hole. Knowing more about galactic black holes will help astronomers learn more about the evolution of galaxies and the relationship between galaxies, black holes, and quasars. Astronomers Holland Ford, Richard Harms, and colleagues have used data from the Hubble Space Telescope to develop strong evidence that a black hole exists in the center of the elliptical galaxy M87 in Virgo. Ford and Harms have shown that a small mass, fast rotating disc lies at M87’s heart.(Powell 12) There is also a black hole Peters 3 that is eating the Milky Way. The core of the Milky Way galaxy, 180 quadrillion miles from Earth, exerts enough force to hold together a system of 100 billion stars. Astronomers trying to determine the origin of this force think they may have found the answer-a black hole at the center of the galaxy with the mass of three million suns, sucking in matter and emitting odd radio waves and other signals. Astronomers first noticed a glow of gamma radiation at the center of the galaxy in the 1970’s. But the most convincing evidence was a motionless source of radio waves that were detected at the center of galaxy. All of these factors indicate a supermassive center that is absorbing matter into it’s gravitational field at great speed.(Sawyer 38) Using a series of radiotelescopes stretching 5,000 miles across the United States from the Virgin Islands to Hawaii, an international team of astronomers have discovered strong evidence of an incredibly powerful black hole as massive as 40 million suns. The findings, presented to the American Astronomical Society in Tucson Wednesday and published today in the journal “Nature,” is considered the strongest evidence yet of the existence of black holes. It is difficult to prove the existence of black holes primarily because, by definition, they can never be seen. At best, scientists can only study the that would be expected in the surrounding territory if in fact a black hole is there. By several accounts, astronomers projects from the 1980’s have come closer than any of the others. Scientists lust after evidence of black holes because they are among the most mysterious objects in the universe, devouring everything within their gravitational reach. Their immense pull is believed responsible for swirling masses of stars that radiate brilliantly across the heavens. A fuller understanding of black holes is considered

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