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[MUSIC]

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Joan Cartan-Hansen, Host: Our 
sun is a medium-sized, middle

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aged yellow dwarf star.

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Stars are huge, glowing balls of 
mostly burning hydrogen gas.

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They vary in size, temperature, 
color and brightness.

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The color of a star depends upon 
its temperature.

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Cooler stars appear red and 
hotter stars glow bluer.

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Stars begin life in clouds of 
hydrogen and dust.

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Material clump together, packing 
tighter and tighter and hotter

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and hotter.

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Eventually, the star begins to 
burn brightly.

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Stars like our sun live for 
billions of years.

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Our star is about four billion 
years old and has enough fuel

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for approximately five to eight 
billion more.

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Stars do eventually die.

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Some turn into black holes.

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Others collapse and explode.

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Becoming a supernova.

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The brightest star in our night 
sky is Sirius.

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It's 8.6 light years away.

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That means the light from Sirius 
has been traveling for 8 point 6

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years.

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So, when you look at the stars 
at night, you're looking into

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the past.

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For more information about 
astronomy, check out the science

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trek website.

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You'll find it at science trek 
dot org