astronomy

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Across
  1. 3. used to find distance to a galaxy
  2. 6. occurs when light from a distant object passes a nearby massive object
  3. 8. cloud of turbulent gas
  4. 10. a flattened cloud of billion stars
  5. 11. the orbital speed of visible stars
  6. 13. relation between apparent velocity of recession and distance
  7. 14. first called quasi-stellar
  8. 15. invisible stuff in space that has gravity
Down
  1. 1. contains most of the galaxy's stars
  2. 2. highly luminous nuclei with peculiar spectra
  3. 4. to find the mass of the galaxy
  4. 5. a measurement of distance
  5. 7. difficult to observe directly
  6. 9. triggered by a burst of star formation
  7. 12. contains a thousand or more galaxies