Stars and Galaxies

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Characteristics of Stars
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1. The smallest stars are called Neutron Stars,
they are about 16 kilometers across.
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2. Stars smaller than the sun, as small as the
diameter of Asia are called White Dwarf Stars.
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3. Our sun is a Medium Star and has a diameter
of about 1.4 million kilometers, about 109 times
as wide as the earth.

(Our Sun)
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4. Stars with diameters about 10 to 100 times as
large as the sun are called Giant Stars.
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5. Super-giant Stars have a diameter approx.
1000 times as large as the sun.
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A. Using a spectroscope, scientists have
determined that most stars have the same
composition. Hydrogen (H) makes up about 60-80
of a stars mass. Helium (He) makes up most of
the remaining mass along with Oxygen (O), Neon
(Ne), Carbon (C) and Nitrogen (N).
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B. The sun has a surface temperature of about
6000C. Its core is approx. 15,000,000C. The
hottest stars are believed to have a surface
temperature of 50,000C.
C. Hertzsprung-Russell diagram - Chart that
shows the relationship betweeen the absolute
magnitude and the surface temperature of stars.
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D. Parallax - The apparent change in position of
a star.
1. A parallax can be used to accurately
determine the distance of stars up to 100 light
years away.
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2. The distance of stars 100 light years to 7
million light years is determined using magnitude
(brightness).
3. For stars further than 7 million light years,
the amount of red shift is determined using a
spectrascope.
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The Most Important Star.Our Sun
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A. Three layers make up the suns atmosphere, and
one layer makes up its interior.
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1. Corona - The outermost layer of the suns
atmosphere, temperatures can reach 1,700,000C.
2. Chromosphere - The middle layer of the suns
atmosphere, temperatures average 27,800C.
3. Photosphere - The innermost layer of the
suns atmosphere, temperatures do not exceed
6000C.
4. Core - The center area of the sun,
temperatures can reach up to 15,000,000C.