The Unverse

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Across
  1. 6. A good orbit for a spy satellite
  2. 7. A key vector quantity
  3. 8. Everything!
  4. 10. A good orbit for a communication satellite
  5. 12. Scientist who first observed moons orbiting Jupiter
  6. 15. This follows a main sequence star
  7. 16. An object that emits no light
Down
  1. 1. The type of nuclear reaction inside stars
  2. 2. The penultimate stage for a massive star
  3. 3. Comets have this shape orbit
  4. 4. Earth in the centre of the solar system
  5. 5. The fuel used by stars
  6. 9. Sun in the centre of the solar system
  7. 11. Evidence of the expanding universe
  8. 13. The Earths orbit is almost perfectly...
  9. 14. This causes a nebula to shrink