Universe crossword

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Across
  1. 4. particle with a negative charge
  2. 6. balls of hot gas – mostly hydrogen, with some helium and small amounts of other elements held together by gravity
  3. 8. of space and time and the matter and energy they contain
  4. 9. by which two light atomic nuclei combine to form a single heavier one. The process releases massive amounts of energy called a photon
  5. 10. of matter consisting of charged particles. The charged particles are positive ions and free electrons
  6. 13. cloud of concentrated gas and dust in space
  7. 15. Planet
  8. 16. particle with a positive charge
  9. 17. of light and heat emitted from a nuclear fusion reaction
  10. 19. Milky Way is the galaxy where our solar system is found
Down
  1. 1. be spherical, orbit the sun, and have cleared objects out of its orbital path
  2. 2. giant
  3. 3. Giant
  4. 5. Way
  5. 7. Fusion
  6. 10. particle with no charge
  7. 11. solid rocky cores surrounded by a thick layer of water, ammonia, and methane.
  8. 12. force between objects that have mass
  9. 14. planet mostly composed of helium and/or hydrogen. Consist of swirling gases above a solid core
  10. 18. of billions of stars brought together by gravity