Astronomy crossword

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Across
  1. 5. A large group of smaller galaxy clusters or galaxy groups
  2. 7. The outer asteroid belt of the solar system is known as the ______ belt
  3. 9. Cosmic clouds of gas and dust
  4. 10. The distance at which one astronomical unit subtends an angle of one arcsecond
  5. 12. Considered the smallest structure in the universe, being roughly 1.2×10^-10 m in radius
  6. 14. The most common/abundant atom in the universe
  7. 16. Which planet has a diameter 11 times the diameter of Earth?
  8. 17. The Number of planets in the Solar System
Down
  1. 1. An astronomical object of very high luminosity found in the centres of some galaxies and powered by gas spiraling at high velocity into an extremely large black hole
  2. 2. Milky Way is falls under this classification of galaxy types
  3. 3. Energy emitted as electromagnetic radiation persecond
  4. 4. Second most common/abundant atom in the universe
  5. 6. The fastest speed in the universe is the speed of _____
  6. 8. Pluto is classified as a _____ planet
  7. 11. The Earth’s radius is about 3.666 times larger than the ____
  8. 13. Cloud which marks the border of the Solar System
  9. 15. Which planet has a radius of 6,378 km?