on. 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 newtypes 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 blackholes 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 inthe center of the elliptical galaxy M87 in Virgo. Ford and Harms have shown that a small mass, fast rotating disc lies at M87s heart.(Powell 12) There is also a black holethat is eating the Milky Way. The core of the Milky Way galaxy, 180 quadrillionmiles 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 millionsuns, sucking in matter and emitting odd radio waves and other signals. Astronomersfirst noticed a glow of gamma radiation at the center of the galaxy in the 1970s.But the most convincing evidence was a motionless source of radio waves that weredetected at the center of galaxy. All of these factors indicate a supermassive centerthat is absorbing matter into its gravitational field at great speed.(Sawyer 38) Using a series of radiotelescopes stretching 5,000 miles across the United Statesfrom the Virgin Islands to Hawaii, an international team of astronomers have discoveredstrong evidence of an incredibly powerful black hole...
