Astronomical puzzle

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Across
  1. 3. , The star you can see when you look up north
  2. 7. , The only planet that is deemed livable
  3. 8. , everything in the universe
  4. 9. , A cylinder shape object that can propel to a high distance
  5. 11. , The first planet of our solar system
  6. 12. , nonluminous material that can't be seen
  7. 14. , An extremely luminous and active galactic nucleus
Down
  1. 1. , The biggest planet in our galaxy
  2. 2. , The 4th planet in our universe
  3. 4. , The study of stars
  4. 5. , the shape stars make
  5. 6. , A celestial object containing ice and dust in space
  6. 10. , The way a planet or moon goes around something
  7. 13. , The name of our universe
  8. 15. , The closest galaxy to us