The Life Cycle of a Star

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Life Cycle of a Star Our Sun is a perfect example of a star, and there is an incredible amount of stars in the Universe. It is a star among hundreds of billions of stars within our Milky Way Galaxy, and our galaxy is one of billions of galaxies in the universe. Stars live for a very long time; millions, billions, or tens of billions of years so we can never really observe the life of a star; its birth, life, and death. In determining the life cycle of a star, astronomers observe many of the billions of stars around us and see them at different stages of life, therefore piecing together a star's evolution. A star is born from clouds of gas and dust called nebulae found in interstellar space. Nebulae are composed mainly of hydrogen and helium, but also contain traces of heavier elements. It is uncertain as to how the very first stars were created. What is known is that after the first stars were formed, they began to generate energy which in turn heated up its surrounding gas in the nebula. The gas, once heated began to expand and its pressure and density increased. A few of the very first stars were massive and short lived, quickly finishing their supply of fuel and exploding. From theses explosions, hot gas was emitted into the surrounding nebula increasing the pressure and density even more. When the pressure and the gas density got too high, the gravity between molecules was able to bring its particles together. Matter then began to separate and fall into common centers. When the dust and gas was united, particles accelerated under its force of gravity and began colliding with one another. These collisions caused a small area in the cloud to become very hot and dense. This heat caused the molecules t... ... middle of paper ... ...is between millions to tens of billions of years, but being able to view many of these stars much like the observation of a human life, astronomers have been able to produce a stars life cycle. Some of the observations and conclusions are merely theoretical, such as the notion of a black hole. However, just because we cannot see it does not mean that it is not there. Works Cited Bennett, Jeffery, Megan Donahue, Nicolas Schneider, Mark Voit. The Solar System: selected chapters from The Cosmic Perspective Third Edition. San Francisco: Pearson Education Inc., 2004. Encyclopedia Britannica Concise CD-Rom. 2001. Encyclopedia Britannica Inc. Thompson, Graham R., Jonathan Turk. Earth Science and the Environment Second Edition. Orlando: Harcourt Brace & Company, 1999 Slides and notes from lectures in class on chapter 16, 15 Aug. 2005.

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