1. I saw a UFO.
2. We were visited by aliens.
3. Do you believe in Martians?
4. What is beyond the cosmos?
5. They found signs of an alien civilization.
6. We have been invaded.
7. My classmate was abducted by aliens.
8. Aliens come in peace.
9. The planets are unexplored.
10. Earth is a lush and fertile planet.
11. Heaven is on earth.
12. Our planet has one moon.
13. Mars is the red planet.
14. Astronauts landed on the moon in 1969.
15. Powerful telescopes allow scientists to study the planets.
16. New planets are still being found.
17. I like astronomy.
18. Humans may one day colonize other planets.
19. The universe is expanding.
20. UFO sightings occur all the time.