Word: sun
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Dates: during 1980-1989
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There is another possible scenario: if a star is a minimum of 30 to 40 times as massive as the sun, its gravitational collapse could be so violent that it may never become a supernova at all. Instead of bouncing back at the instant of maximum scrunch, the core continues its collapse indefinitely, forming a bizarre object of infinitesimal size and nearly infinite density, with a gravitational field so intense that light itself cannot escape -- a black hole. In effect, the entire, tremendous mass of the star has gone down a cosmic drain...
Robert Frost wrote Fire and Ice in 1923, some four decades before astrophysicists were able to fathom how the sun -- and thus the earth -- would die. Nonetheless, he was basically correct: first fire, then ice. The fire will not be an explosion like the one now brightening the Large Magellanic Cloud; the sun is thought to have only about a tenth of the mass necessary to become a Type II supernova and has no stellar companion to contribute the mass necessary to turn it into a Type I blast. But that will be of little comfort to whatever creatures exist...
Fortunately for the earth's current inhabitants, the sun is enjoying a stable middle age, about halfway between its formation some 4.5 billion years ago and its demise about 5 billion years hence. Its radiation may fluctuate by a few hundredths of a percent here and there (data from the Solar Max satellite indicate that the sun's radiation declined from 1980 through 1985). But solar behavior has never been erratic enough to threaten all terrestrial life with extinction...
...real trouble will begin as the sun nears the 10 billion-year mark, when the thermonuclear fires that have been burning since its birth have fused all the hydrogen fuel in the solar core into helium. As the fuel runs out, the nuclear fire will die down, and the now largely helium core -- which has been kept distended by the heat -- will begin to contract under its own gravitational pull...
...core contracts, however, its internal pressures will rise, forcing the temperature rapidly back up again until the intense heat ignites the unfused hydrogen gas surrounding the core. The interior of the sun will now be hotter than ever, a dense core of incandescent helium surrounded by a thin shell of hot, fusing hydrogen. Over the next few hundred million years, heat from the core will drive surface layers of the sun so far outward that they will cool to about two-thirds of the current 6,000 degrees C surface temperature, and redden. The sun will have become...