vocab words

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Across
  1. 3. our galaxy
  2. 7. galaxies that are not spiral or elliptical
  3. 11. egg shaped rotating galaxy
  4. 12. group of stars
  5. 14. matter we cant see but we know it is there
  6. 15. two stars orbiting each other
Down
  1. 1. the study of the universe
  2. 2. light can not escape the gravity
  3. 4. tens of thousands of stars that are held tightly together by gravity
  4. 5. hypothetical form of energy, may make up as much as 71% of the energy in the universe
  5. 6. a galaxy that only contains a few million stars to a few billion stars
  6. 8. a big group of stars, may contain thousands of stars
  7. 9. nuclear fusion in the stars core produces helium from hydrogen
  8. 10. how astronomers explain the way the universe began
  9. 13. a change in frequency as a obsereveres eyes