Astronomy #3 crossword

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Across
  1. 2. rapidly fast spinning magnetized neutron star
  2. 6. high energy subatomic particles traveling nearly the speed of light
  3. 9. a star that changes over time
  4. 10. young low mass early star that hasn't gone through fusion yet
  5. 12. red supergiant star
  6. 16. cold dense interstellar cloud of gas and dust where stars and planets are born
  7. 18. protoplanet disks
  8. 19. rocky remnants orbiting the sun
  9. 21. a red hyper-giant star
Down
  1. 1. two small irregular clouds
  2. 3. young star with low mass
  3. 4. sun
  4. 5. groups of stars born from the same interstellar clouds
  5. 7. massive, super giant star
  6. 8. dense collapsed core of a massive star
  7. 11. sudden bright star's luminosity that may dim
  8. 13. class of exceptionally bright pulsating stars
  9. 14. bright open star cluster
  10. 15. dark cool spots on the sun's surface
  11. 17. stars with low mass, luminosity and size
  12. 20. fusion hydrogen stable phase