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Stars
By: Bryent Kaneshiro and Dyani Chock
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A star is a massive, luminous ball of plasma held
together by gravity. At the end of its lifetime, a star
can also contain a proportion of degenerate
matter.
Stars are born when immense clouds of
interstellar dust and gas condense through the
mutual attraction of gravity.
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When condensed material reaches
a critical density, the material becomes a star.
This process is called fusion.
The more massive a star, the faster it uses up
its fuel for fusion. Hydrogen, the most
common element in the universe, is the
primary fuel for fusion in stars. Hydrogen
fusion produces helium.
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After awhile, the star will begin
to exhaust its supply of
hydrogen, and will start feeding
on the helium. This will produce
lithium and heavier elements.
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The lifespan of stars varies from thousands of
years for massive stars to billions for smaller
stars. Our Sun, which is of average mass, is
predicted to live for about 10 billion years.
By knowing the distance, mass, magnitude,
and chemical composition of a star, we can
determine approximately how old it is, when
it was born, and when it will die.
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Scientists determine how old a star is by
looking at its spectra - the data about the
chemical composition of the star that is
revealed in the frequencies of its light. The
more heavy elements present in the star, the
older the star. To get a specific age, the mass
of the star must also be known.
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The amount of light coming from the star can
be measured. The more light there is, the
bigger the star. However, less light arrives
from stars that are further away, so how far
away the star is must be taken into account.
Death of Star
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Massive stars will explode in a supernova,
sometimes producing a blackhole. Tiny stars
will slowly cool and die, becoming cold,
dark, dwarf stars.
Video
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http://www.youtube.com/watch?v=uCzuXRf4rA
Red Dwarf Stars
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Red Dwarf stars can range in size from a hundred times
smaller than the sun, to only a couple of times smaller.
Because of their small size these stars burn their fuel very
slowly, which allows them to live a very long time. Some red
dwarf stars will live trillions of years before they run out of
fuel.
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Red dwarf stars are by far
the most common type of
star in outer space. However
very few stars that you see
in the sky are red dwarfs.
This is because they are so
small and make very little
light.
Yellow Stars
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Yellow stars are medium sized stars are yellow
because they have a medium temperature.
Their higher temperature causes them to burn
their fuel faster. This means they will not live
as long, only about 10 billion years or so.
Near the end of their lives, these medium
sized stars swell up becoming very large.
Blue Giants
Because blue stars are large, and compact, they burn their fuel
quickly, which gives them a very high temperature. These
stars often run out of fuel in only 10,000 - 100,000 years.
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A blue giant is very bright, rare, and they make up many of the
stars we see at night.
Blue giant stars die in a spectacular way. They grow larger just
like the Sun sized stars, but then instead of shrinking and
forming a planetary nebula they explode in what is called a
super nova.
Works Cited
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"Star Lifespan: How Long Does a Star Live?" Suite101.com:
Online Magazine and Writers' Network. Web. 08 Feb. 2011.
<http://www.suite101.com/content/starlifespan-a910>.
"Stars." Astronomy For Kids - KidsAstronomy.com. Web. 08
Feb. 2011. <http://www.kidsastronomy.com/stars.htm>.
"Stars." Imagine The Universe! Home Page. Web. 08 Feb.
2011.
<http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.ht
ml>.
"Well Known Stars And Constellations." WWW2 Webserver.
Web. 08 Feb. 2011.
<http://www2.potsdam.edu/islamma/phys335constellations.
htm>.