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The Milky Way

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Now the Milky Way is not strictly speaking a circle, but rather a belt of a sort of milky color overall (whence it got its name); moreover this belt is neither uniform nor regular, but varies in width, color, density and situation, and in one section is bifurcated. All that is very apparent even to the casual eye . . .

Claudius Ptolemy

Questions to Explore:
  • How do we know that there is gas and dust in interstellar space?
  • How were the size and shape of the Milky Way discovered?
  • Why do astronomers think that much of the Milky Way consists of “dark matter”?
  • Why does the galaxy have spiral arms?
  • Is there a massive black hole at the center of the galaxy?
  • How did the galaxy form, and how has it changed with time?

AstronomyOnline Learning Center

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