WEBVTT

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This is College Physics Answers
with Shaun Dychko.

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We are going to estimate the mass of
the luminous matter

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in the Milky Way galaxy

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we are told there are about
10 to the 11 stars

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and 1.5 solar masses per star

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and we look at the appendix in
the textbook to find

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how many kilograms are in a solar mass,
which is the mass of the Sun.

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So there's 1.99 times 10 to the 30
kilograms per solar mass.

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So this gives us units of kilograms
and there are

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3.0 times 10 to the 41 kilograms of
luminous matter.

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The amount of dark matter is
estimated to be 10 times

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the amount of mass that is luminous

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so we go 10 times the answer for
the luminous mass

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and that's 3.0 times 10 to
the 42 kilograms.