black hole1
An image of the core of the Whirlpool galaxy M51 taken by the Wide Field Planetary Camera onboard the Hubble Space Telescope. It shows an immense ring of dust and gas which is thought to surround and hide a giant black hole, 1 million times the mass of the Sun, in the center of the galaxy. The ring forms an accretion disc of gas, about 100 light years across, falling toward the black hole. The two brighter areas perpendicular to the widest dark lane are two jets of particles accelerated by the black hole. Anyone who has ever watched the launch of a rocket is familiar with the concept that escape from a gravitational field requires the expenditure of energy. The stronger the gravitational field, more energy is required to escape from its clutches. If the rocket has insufficient fuel, it will return to Earth and escape is impossible. Thus, it is not hard to imagine a gravitational field strong enough to prevent the escape of any object with a finite amount of energy. The gravitational force of an object is governed by a combination of the amount of matter it contains and its volume. The more the matter is confined in progressively smaller volume, the larger the gravitational field at the surface of the object.
The absence of light from the massive object suggests it is a black hole. All that has been said so far involves black holes as described by the general theory of relativity. In the centers of some galaxies the stars, gas and dust of the galaxy are moving at very high speeds, suggesting they are being pulled about by the gravity of some very massive object. Thus, to turn the Sun into a black hole, one would have to cram all of its mass into a sphere having about a 3 km radius. It suggested the first link between quantum theory and general relativity and has spawned a host of new ideas which expand the relationship between the two theories. These are the dimensions of the environment surrounding a black hole of stellar proportions. While there are complications in defining the size of a black hole, one can uniquely specify its circumference and thus define a radius as just the circumference divided by 2. Indeed, it seems likely that black holes may reside at the centers of normal galaxies such as our own Milky Way. This "censorship" is what is responsible for the small number of measurable properties of the black hole itself-mass, spin, and charge. However, in the realm of the very small, quantum mechanics has proved to be the proper theory to describe the physical world. While the amount of radiation for any astrophysical black hole is pathetically small, the possibility of it happening at all was revolutionary. If the object was a collection of massive stars, it would shine so brightly as to dominate the light from the galactic center. Indeed, the only aspects of a black hole that may be ascertained from outside are its mass, net charge, and rate of spin. However, the gravitational field of this object, measured at the distance of the Earth, would be exactly that of the present-day Sun. There is at least one other situation where astronomers suspect the existence of a black hole.
Common topics in this essay:
Ultraviolet Explorer,
Karl Schwarzschild,
Space Telescope,
Simon Laplace,
Normally Schwarzschild,
black hole,
Sun Earth,
Sun Sun,
Binary System,
,
mass sun,
gravitational field,
massive object,
black holes,
light beam,
times mass sun,
times mass,
Hubble Space,
hubble space telescope,
light escape,
sun black,
mass times,
black hole mass,
black hole center,
field strong prevent,
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Acceptance Essays
