Space unit

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Across
  1. 4. The scientific explanation of the early development of the universe
  2. 6. A gigantic cluster of 4 to 25
  3. 7. A ball of mass that formed in the centre of the accretion disk
  4. 11. A force created to simulate gravity
  5. 13. The observation that the farther away the faster moving away from earth
  6. 14. Located beyond the orbit of Neptune
  7. 15. The sun's outermost atmospheric layer
Down
  1. 1. A distant spherical cloud of small icy fragments of debris
  2. 2. A massive collection of stars, planets, gas, and dust
  3. 3. A reduced-gravity environment experienced by astronauts
  4. 5. Display of colours when charged particles collude with the atmosphere
  5. 8. The distance that light travels in one year
  6. 9. A region of complete shadow, which a complete eclipse will occur
  7. 10. A celestial body that orbits the sun, nearly round
  8. 12. The average distance between Earth and Sun