ASTRONOMY

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Across
  1. 2. ______ ga ga
  2. 5. the first person to suggest the earth was round
  3. 7. we use it to see our bones
  4. 8. we are studying it currently
  5. 10. stars are made of ____
  6. 11. what are comets made of
  7. 13. it protects us from harmful rays
  8. 15. we use it to see heat
  9. 16. they have a tail
  10. 18. it is commonly used for invisible ink
  11. 19. what planet are we on
  12. 20. our planet is covered mostly with ______
Down
  1. 1. gamma has the shortest _________ and radio the longest
  2. 3. we measure brightness in _______
  3. 4. the distance from the earth to the sun is 1 __
  4. 6. has the shortest wavelength
  5. 9. it is commonly mentioned with global warming
  6. 12. the light we can see
  7. 14. most of us have one to cook things
  8. 17. our galaxy is a ______ galaxy