Cosmos

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Across
  1. 4. Force/bending of spacetime
  2. 7. Has a trunk
  3. 10. Methane kingdom
  4. 12. Largest volcano in the Solar System
  5. 13. Large marsupial
Down
  1. 1. Man's best friend
  2. 2. Xray observatory
  3. 3. Flying mammal
  4. 5. Medium that was considered to fill space inbetween planets
  5. 6. Likes to chase mice
  6. 8. Evidence that nuclear fusion is still taking place inside Sun's core
  7. 9. Compton can observe
  8. 11. A planet calculated to be between Mercury and Sun, but turned out true
  9. 12. Night should be as bright as day