Out of this World

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Across
  1. 2. type of Galaxy
  2. 5. first person to journey into outer space
  3. 8. space telescope
  4. 10. science of mapping stars and planets
  5. 11. a neutron star
  6. 13. Hg, a planet
  7. 14. seventeenth century astronomer
  8. 15. first person to walk on the Moon
  9. 16. once a planet, now a dwarf planet
  10. 18. "falling" or "shooting" star
Down
  1. 1. 20th century cosmologist
  2. 3. "evening star"
  3. 4. famous comet
  4. 6. small rocky body orbiting our sun
  5. 7. nearest major galaxy to the Milky Way
  6. 8. gas that fuels our sun
  7. 9. a moon of Jupiter
  8. 10. study of celestial objects
  9. 12. 'God of the sea' and a planet
  10. 17. astronomical body that orbiting a planet