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In Search of Black Holes
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# : |
17757 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
6 / 1990 |
2,737 Words |
| Author
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Seth Shostak
Seth Shostak, who currently resides in Mountain View,
California, has spent most of his career as a research radio
astronomer. |
Imagine a visit to a stellar grave. Not long ago this was one of the bright places of the universe. A mighty inferno burned there, shining with 10,000 times the light of the sun. Sadly, prodigious luminance has a price, and this celestial giant soon exhausted its nuclear fuel. Then, in a death throe so brief as to be but an eye-blink in the history of the galaxy, it became what now les before you: an apparent void in the starlit blackness of space.
A black hole is the ultimate in garbage disposal, a landfill in which every deposit is meticulously broken down and compacted. It is a cosmic trash masher so brutally efficient that nature has even conspired to hide it perfectly from our view. Its massive contents are out of sight, out of mind, and for all practical purposes, out of this universe.
Although astronomers have spent a half-century speculating on the fraction and behavior of black holes, these bizarre denizens of the celestial menagerie remain elusive. While there are about a dozen objects researchers think might be black holes, they have yet to confirm a single example. This is both disappointing and disconcerting, for despite their invisibility, black holes should be straightforward to find.
The Fate of Stars
The easiest way to locate a black hole is to sit around and wait for a big star to die. As death approaches, the force of gravity suddenly gains the upper hand in deciding a star's destiny. Gravity, the attraction that all matter has for other matter, is the feeblest of the physical forces, of far less magnitude than the familiar attraction and repulsion of charged particles, or the even stronger nuclear forces at work in the centers of atoms. But while it may be nature's weakling, gravity is inexorable, strongest when near a center of mass but effective even at great distances. While alive, a star can easily ward off gravity's attempts to cause it to sink under its own weight. The enormous temperature of the star's constituent gases, acting much like the steam in a kettle, generates pressure capable of staving off collapse.
In this way, every star from here to the farthest galaxies manages to strike a balance between the expansive pressure of its burning gas and the contracting pull of gravity. It is an equilibrium that, in the case of medium-sized stars such as the sun, will be maintained for billions of years. But the equilibrium is nonetheless temporary; it is a bargain with the devil. All stars ultimately burn
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