Cosmic Conundrum

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Across
  1. 3. Astronomical distance unit
  2. 6. The closest star to Earth
  3. 8. A group of stars forming a recognizable pattern
  4. 11. Spacecraft for exploring space
  5. 12. A cloud of gas and dust in outer space
  6. 14. A massive explosion in space
  7. 15. Mars' neighboring planet
Down
  1. 1. A small, icy body that orbits the Sun
  2. 2. hole A hypothetical massive object with gravity so strong that nothing, not even light, can escape from it
  3. 4. The study of celestial objects and phenomena outside the Earth's atmosphere
  4. 5. A small, rocky object orbiting the Sun
  5. 7. cluster A cluster of stars held together by gravitational attraction
  6. 9. A massive black hole at the center of a galaxy
  7. 10. Large celestial body orbiting a star
  8. 13. Giant cosmic structures made up of stars, gas, dust, and dark matter