chapter19 - Chapter 19 Our Galaxy 19.1 The Milky Way...

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Chapter 19 Our Galaxy
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19.1 The Milky Way Revealed Our goals for learning What does our galaxy look like? How do stars orbit in our galaxy?
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What does our galaxy look like?
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The Milky Way galaxy appears in our sky as a faint band of light
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Dusty gas clouds obscure our view because they absorb visible light This is the interstellar medium that makes new star systems
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All-Sky View
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We see our galaxy edge-on Primary features: disk, bulge, halo, globular clusters
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If we could view the Milky Way from above the disk, we would see its spiral arms
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How do stars orbit in our galaxy?
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Stars in the disk all orbit in the same direction with a little up-and-down motion
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Orbits of stars in the bulge and halo have random orientations
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Thought Question Why do orbits of bulge stars bob up and down? A. They’re stuck to interstellar medium B. Gravity of disk stars pulls toward disk C. Halo stars knock them back into disk
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Thought Question Why do orbits of bulge stars bob up and down? A. They’re stuck to interstellar medium B. Gravity of disk stars pulls toward disk C. Halo stars knock them back into disk
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Sun’s orbital motion (radius and velocity) tells us mass within Sun’s orbit: 1.0 x 10 11 M Sun
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Orbital Velocity Law The orbital speed ( v ) and radius ( r ) of an object on a circular orbit around the galaxy tells us the mass ( M r ) within that orbit M r = r ´ v 2 G
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What have we learned? What does our galaxy look like? Our galaxy consists of a disk of stars and gas, with a bulge of stars at the center of the disk, surrounded by a large spherical halo How do stars orbit in our galaxy? Stars in the disk orbit in circles going in the same direction with a little up-and-down motion Orbits of halo and bulge stars have random orientations
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Our goals for learning How is gas recycled in our galaxy? Where do stars tend to form in our galaxy?
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chapter19 - Chapter 19 Our Galaxy 19.1 The Milky Way...

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