Treasure Hunt

1234567
Across
  1. 3. Things that revolve around another object in space.
  2. 6. Two objects that attract each other due to their mass.
  3. 7. A source of energy that is endless.
Down
  1. 1. Trees cannot produce fruit without them.
  2. 2. We will run out of this in 39 years.
  3. 4. This is caused by the Moon's gravitational pull on Earth.
  4. 5. Our Solar system is one of many millions of solar systems inside this.