Calling planet Earth-What's out there ?

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Across
  1. 3. an artificial body placed around a planet
  2. 5. people trained to travel to space
  3. 6. the power that attracts bodies to the Earth
Down
  1. 1. includes the sun, eight planets & their moons
  2. 2. Earth, Mars, Neptune, are examples of this word
  3. 4. the collection of billions of stars