1920: The Shapley-Curtis Debate The Evidence

• Curtis

  • In the plane of the galaxy, stars seem to become less common as you get farther away, so the sun is at the center of the galaxy. The stars appear to end about 30,000 light years away.
  • Stars in globular clusters are faint, so the clusters are closer than Shapley estimates.
  • The spectrum of a spiral nebula looks like the spectrum of a cluster of stars rather than light emitting gas, so it is logical to assume they are great clusters of stars.
  • All other nebula types are concentrated near the plane of the Galaxy

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