Crossword Puzzle Clue

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Across
  1. 3. Stars cooler than the sun, emitting less energy per square meter but have a higher luminosity and greater surface areas.
  2. 7. A rocky object orbiting the sun
  3. 8. When an asteroid lands on a planet
  4. 9. A group of stars that are positioned close enough to be held together by gravity
Down
  1. 1. Two stars that rotate around a common center of mass
  2. 2. The remnants of old stars
  3. 4. A creation of stars, gas, and dust held together by gravity and containing billions of stars.
  4. 5. A large astronomical body that is neither a star nor stellar remnants
  5. 6. Irregular objects a few km across, composed of gases, rock, and dust
  6. 9. Formed when gravity causes the gas in a Nebula to condense