The Life Cycles of Stars
In the universe, there are hundreds of billions of stars. They are formed when gas and dust from space "clump" together. As the mass grows larger, gravity takes over and a core begins to form. The core becomes extremely dense and this compaction causes temperatures within it to rise to the point where nuclear fusion (the burning of hydrogen in a chain reaction) can begin. The heat generated by fusion can reach 24 million degrees F (Fahrenheit). "That amount of heat keeps the outer gas shell expanding while the ultra-dense core keeps from collapsing under its own gravity. The star is said to be in "equilibrium" or on the "main sequence". This is the point where a star spends most of its life." (Aspire.Cosmic-Ray.org, Stars, Main Sequence).
If in the formation of a star not enough heat is generated in the core to begin a fusion reaction, it is known as a Brown Dwarf. The stars core burns different gases or materials, but soon dies off to be a cold mass in space which is very difficult to detect since they give off no luminosity.
Another category of star is the Yellow Dwarf. The most known star to all of us in this group is our Sun. With a diameter of 864 thousand miles, it is a comparatively small star. The surface temperature is 11 thousand degrees F., with a core temperature of 24 and one-half million degrees. Our Sun is currently halfway through its 10 billion year life. The Sun is brighter than 85% of the stars in the galaxy, most of which are Red Dwarfs.
Red Dwarf stars make up the majority of stars in the universe. They are still "main sequence" stars, or stars in equilibrium, but they have a much cooler surface temperature than the Sun around five thousand nine hundred degrees F. Due do the relatively cool surface temperatures, the star glows red. Since Red Dwarfs are smaller in size, they can burn more fuel than larger, more massive stars and are much more stable. This gives them a much longer life, sometimes as long as...
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Life Cycles of Stars. Retrieved July 20, 2007 from http://library.thinkquest.org/17940/texts/star/star.html
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Betelgeuse. Retrieved July 22, 2007 from http://en.wikipedia.org/wiki/Betelgeuse
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