Chapter 15 - Our Milky Way Galaxy Chapter 15 Chapter 15...

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Our Milky Way Galaxy Chapter 15
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Chapter 15
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Milky Way Galaxy • Faint band of light, slicing through the constellations of Sagittarius, Cygnus, Perseus and Orion. • Greeks called it flowing ribbon of milk. • Our Galaxy ( galactos , Greek for milk) holds more than 100 billion stars and is just one among tens of billions of galaxies in the observable universe.
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What makes up the ‘milky’ band of light of our galaxy? A. distant glowing white interstellar clouds B. many distant stars too far to resolve with our eyes C. the asteroid belt D. white dust particles in our solar system Survey Question
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What makes up the ‘milky’ band of light of our galaxy? A. distant glowing white interstellar clouds B. many distant stars too far to resolve with our eyes C. the asteroid belt D. white dust particles in our solar system Survey Question
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What are the dark breaks in the ‘milky’ band of light of our galaxy? A. dusty clouds of gas that block visible light B. empty breaks in the distribution of distant stars C. rips in the fabric of space-time D. interstellar material from which stars form E. both A & D Survey Question
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What are the dark breaks in the ‘milky’ band of light of our galaxy? A. dusty clouds of gas that block visible light B. empty breaks in the distribution of distant stars C. rips in the fabric of space-time D. interstellar material from which stars form E. both A & D Survey Question
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Our Milky Way Galaxy Artist’s conception!
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Evidence: All-sky image of Milky Way MW has two major spiral arms (traced here by molecular clouds and radio waves): Perseus and Scutum-Centaurus Arms and several “partial”.
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Evidence: All-sky image of Milky Way Which spiral arm do we belong to? - Orion Spur
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Face on view of the galaxy shows its spiral structure Spiral arms are made of clouds of new stars and debris of the earlier generation of stars . What would be the difference in stellar composition of stars found in the spiral arms (Pop I) and halo (Pop II)?
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Edge-on View The disk’s thickness is 1/100 of the disk’s diameter.
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How do we know where we are in the Milky Way? Related question: how do we know how big the Milky Way is? 1755: Immanuel Kant proposed that our galaxy is a disk of stars, including the Sun! 1785: William Herschel made a map of individual stars he could see - inferred the distance by assuming they were all the same luminosity.
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Suppose you tried to determine where we are in our home galaxy by counting individual stars in different directions. You would estimate that we are A. at the center of the Galaxy. B. in an arm of the Galaxy. C. near the edge of the Galaxy. Survey Question
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Suppose you tried to determine where we are in our home galaxy by counting individual stars in different directions. You would estimate that we are A. at the center of the Galaxy.
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