dipper@utastro.UUCP (Debbie Byrd) (03/09/86)
The stars seem eternal -- but they don't last forever. We'll talk more about the death of stars in just a moment. March 9 The Death of Stars The death of a star depends pretty much on one thing -- mass -- or the amount of matter contained in the star. We know stars that range from about five pr cent of the sun's mass -- all the way up to at least a hundred times as massive as our sun. The most massive stars are brightest. But they don't live as long as the dimmer, least massive stars, which shine for many billions of years before they finally use up their thermonuclear fuel -- collapse on themselves -- and begin to fade away. The most massive stars can only shine for millions of years, instead of billions. Like spendthrifts, these huge stars use up their fuel in a rush. They forestall their final end by becoming red super giants -- which burn increasingly more complex thermonuclear fuels. But, ultimately, all their fuel is gone. After they exhaust their fuel, many stars end up as collapsed objects. But the more massive the star, the more bizarre object it becomes. A star as massive as our sun will collapse to become a white dwarf -- a very dense object about the size of the Earth. A star slightly more massive will collapse even further -- to become a super dense neutron star only a few miles in diameter. But extremely massive stars that start as brilliant giants undergo the most complete ultimate collapse. Such a star will collapse to a point where all its former colossal bulk is contain in a single point -- a point we can only know in theory. This kind of star is called a black hole. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin