The Life Cycle Of A Star Essay — страница 2

categorized in two ways: ?stars with initial masses of less than about eight solar masses?(nasa.gov (1)) and ?stars with initial masses greater than about eight solar masses?(nasa.gov (1)). The stars with initial masses of less than about eight solar masses, ?small stars? will end by ejecting planetary nebulae. The planetary nebula is an expanding shell of gas ejected by a red giant late in its life. A red giant is what the star is called when it still is burning nuclear fuel on the surface of the star rather then the core. A small star exists as a red giant before it completely burns out of nuclear fuel and condenses to a density of ?about a million to 10 million times that of water?(nasa.gov (2)) at which point the dead star is called a white dwarf. A star with an initial mass

of greater than about eight solar masses, ?large star?, dies a completely and much more extravagant death. A large star dies by exploding, this explosion is called a supernova. A supernova is an awesome explosion that lasts for a very short time just before the star completely dies. When the supernova occurs, it releases as much light as an entire galaxy. After the supernova occurs, one of two things may happen. Either the star will become what is known as a neutron star, or it will become a black hole. The neutron star bares its name because it consists primarily of neutrons. The neutron star is significant because of its density. It weighs about 1.4 – 3 times as much as our sun, yet is only 12 miles in diameter. That makes it ?100 to 1000 trillion times the density of

water?(nasa.gov (2)). The other alternative is for the supernova to become a black hole. A black hole is a phenomena not entirely explained in our universe. One theory is that a black hole is much like a cone, or a funnel, that leads to spot in the universe that has no volume but infinite mass, known as a singularity. This theory defies all of the laws of physics and relativity. But, black holes are very difficult to study. They are very difficult to observe because no light is emitted from them; also any light that comes near a black hole is sucked in because the gravitational force of the black hole is so great it pulls in even the basic element of light, the photon. Supernovae are believed to be responsible for most of the matter that goes into the creation of new stars. Like

a human being laid to rest, becoming part of the earth only to rise again, as food for another human?s life. And so the life cycle continues. Bibliography Neufeldt, Victoria, Webster?s New World Dictionary; Macmillian General Reference New York, NY; ?1995, 1989 Nasa.gov (1) http://observe.ivv.nasa.gov/nasa/space/stellardeath/stellardeath_2.html Nasa.gov (2) http://observe.ivv.nasa.gov/nasa/space/stellardeath/stellardeath_6.html#PLANETARY_NEBULA 338