Sections Review

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Vocabulary

dark matter galactic cannibalism Hubble Law
poor cluster rich cluster rotation curve
starburst galaxy supercluster velocity dispersion

Review Questions

  1. Why must the distance to a galaxy be known first before you can measure such basic properties of the galaxy such as its luminosity, mass, and size?
  2. What are the various ways you can find distances to the galaxies?
  3. What do you find when you plot the redshifts of the galaxies vs. their distance from us? How does the speed of most galaxies vary with increasing distance from our galaxy?
  4. How does the Hubble Law show that the universe is expanding?
  5. How does the Hubble Law show that all of the galaxies are moving away from each other and that astronomers in every galaxy will see the same Hubble law?
  6. How can you measure the masses of galaxies?
  7. What is it about the motions of the stars in galaxies that indicates a large amount of dark matter is present?
  8. What is a cluster of galaxies? Are we in one? What is the nearest large cluster of galaxies to us?
  9. Why are collisions of galaxies much more common than collisions of stars?
  10. How are spiral galaxies formed?
  11. What two ways are there to create an elliptical galaxy?
  12. What kind of galaxy is typically found near the center of a large cluster of galaxies? Why is that kind of galaxy so big?
  13. Why is the spatial distribution of clusters of galaxies sometimes described as a foamy structure or like edges of soap bubbles? How do we know that the clusters have this spatial distribution?

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last updated: 25 May 2001

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Author of original content: Nick Strobel