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How Stars Shine

How Stars Shine - The Sun is a relatively regular star •...

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How Stars Shine Dark Energy makes up 73% of the universe, 23% dark matter, and 4% atoms How do you get masses of stars? o Over 50% of the stars you see are actually party of systems of multiple stars many are part of a double o Can find the masses by observing their orbits m1r1 = m2r2 Orbit their common center of mass High mass star is much closer to the center of mass Kepler’s second Law F = Gm1m2/d^2 Mass-Luminosity Relationship o main use of binary stars is to get stellar masses o Have to be main-sequence stars o mass-luminosity relation implies that massive stars have short lives compared with low mass stars they have more fuel, but they burn very quickly L = M 4
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Unformatted text preview: The Sun is a relatively regular star • Determining the Age o Stars that are still in clusters are the easiest way to determine age o globular cluster – millions of stars held together in a relatively small area – a few 10s of light years wide all the stars are formed from the same cloud of gas, around the same time, and at relatively the same distance O-type stars only live for a few million years Sun = 10 billion years M Star is greater than 100 billion years The “turn-off point” of the main sequence gives Age of cluster Find age by looking at the most massive star – If G types had burnt out be at least 10 billion years old...
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