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Astro - Star'S Life

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Autor:  anton  15 November 2010
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Introduction

Stars make up the majority of what we see in the night sky. For all practical purposes the universe contains almost an infinite number of stars (billions upon billions….). Stars have been studied for as long as humans looked up at them. They are classified, categorized, and we have seen images of both the beginning and ends of stars. This paper will discuss the nature of the birth to the end-of-life cycles of stars.

Electromagnetic Waves

The universe is an expanding amalgam of gases, particles, dust, heat, cold and everything that is around us. One Major basis of what we see and measure in science are electromagnetic waves. They make up an emission (either natural or man-made) that depending on the cycle of the wave (how close they are together) resides on a spectrum. At the low end of the septum are radio and micro-wave types of waves. At the higher end are gamma and beta form of waves that are so tight that that cycles are an atoms width or less apart.

Of the entire spectrum only a very small swath makes up what we can see with our eyes. The rest can be measured and seen by various instruments and other devices. Observing stars is not only done by the means of seeing them, but by also observing the waves they put out – Xrays, Gamma rays and other waves we do not see with the naked eye.

The American Heritage Dictionary defines the universe as:

“All matter and energy, including Earth, the galaxies and all therein, and the contents of intergalactic space, regarded as a whole. It is known that the universe is expanding rapidly, and that all other galaxies are "rushing" away from us. The universe is made up of many different structures arranged in a fairly well-defined hierarchy”

Stars, which are formed by the compression of gases and other matter from nebulous materials in space are considered the smallest aspect of the hierarchy of the Universe. That is they are super-abundant in nature but from a hierarchal perspective they are the fundamental element that make up an ever expanding group of universal elements:

Stars, Star Clusters, Galaxies, Galaxy groups, Galaxy clusters, Walls/Voids

Star Characteristics

Stars at various stages of their life cycle have very different structures; however, stars in the main sequence grouping of stars have a general structure that is roughly the same as our own sun. Stars, like our sun, are made up of hydrogen and helium gases, which undergo nuclear fusion in a hot, fiery core. The core, at a temperature of 15,000,000°C, fuels the star and is made entirely of gases. From the core, energy moves out toward the surface of the star through the convection zone, an area in which gas rises and sinks. A star’s surface, its outer layer of gases, is much at about 5000 ° C. The chromosphere is a thin and layer of gas outside the surface of a star. The corona is an even thinner layer of gas that surrounds the chromosphere. It is much hotter than a star’s surface at over 2,000,000°C. A star creates a continual a solar wind, which is a steady stream of ions and electrons. The fusion reaction and magnetic turmoil on a star can cause eruptions or flares to leap far from the star’s surface.

H-R Diagram

The Hertzsprung-Russell (H-R) classification of stars puts into perspective the relative size, luminosity, mass and temperature of different star classifications. Our sun is the reference point of which all other stars are compared to. These classifications allow us to compare and contrast the general characteristic of a star and determine and estimated destiny of the life cycle of a particular star.

Star’s Life Cycle

It is speculated that all stars are born the same way. Starting as clouds of dust, hydrogen, and helium in a formation called nebulae. Over time (millions of years perhaps) this material compresses into a mass none as a protostar. At this point a protostar star is the gathering of the materials that will ultimately produce energy. As the temperature increases in this “pre-star” nuclear fusion begins in it’s core. At This is the point where the star’s fusion life begins. The stars' sizes and eventual fates are determined by the heat, size, shape, and location of the original protostars. Stars formed in this manner generally begin their lives in clusters, but then are influenced by other objects around them and slowly drift apart. Mature stars are classified and their origins revealed by their masses, sizes, temperatures, colors, and magnitudes.

Depending on the type of star (size and classification) it will go through similar phases but may end-up with a different fate. Giants and Super giant stars are very hot and expend their hydrogen full quickly by stellar standard (100million to 1 billion years). As the fuel starts to dry up the star will expand into a red super giant star. These Red Super giants are unstable and usually go super nova leaving either a neutron or pulsar star in its wake or if the star was superior in size and mass a black hole can form.

For smaller less massive stars the life span is much longer 10-15 billion years, and the fate is much different. When the hydrogen fuel is used up the star will grow in size (like their super giant counter parts) and these expanded stars will extend their outer layers to form planetary nebulae. At the center of such a nebula will remain a small white dwarf (about the size of Earth), which is very dense and contains most of the original mass of the star. White dwarves continue to radiate heat from the billions of years of fusion reaction.

Galactic Recycling – Nothing Wasted

For all intensive purposes once matter was create during the big bang nor more or no less has been created or destroyed ever sense. There are caveats to this (such as matter and information collapsing in a black hole) Hawking 1995. But in general everything that ever was will always be. Stars form from the condensation of hydrogen and other materials that over time become so dense they start fusion reactions. Other planetary bodies are created from this cosmic matter to form planets, moons and other objects we see and observe. Over time Interstellar medium becomes reconstituted as other chemicals and elements –started with nothing more than helium and hydrogen is now hundreds of elements and millions upon million of molecules, all produced by stars being born, living, dying and starting anew. When stars go supernova their materials are thrown out far into space, even between galaxies, thus mixing the “genetics” of the universe in an every more intertwined and amalgamated heavier elements and building blocks of new stars and other objects – including life.

References

Electromagnetic Waves and Images Retrevied 2/10/2007 from: http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html

Universe Definition. © 2000 American Heritage Dictionary, Houghton Mifflin, Boston, Ma

The Cosmic Perspective. © 2007, Bennet, Donahue, Schneider, Coit. Pearson Education, San Francisco, Ca

H-R Diagram Retrieved 2/11/2007 from: http://outreach.physics.utah.edu/labs/star_life/hr_diagram.html



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