Astronomy

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Across
  1. 3. A system of millions or billions of stars, along with gas and dust, held together by gravitational attraction.
  2. 7. The curved path followed by a celestial body, such as a planet, around another celestial body, such as a star.
  3. 8. The belief that the Earth is the center of the universe.
  4. 9. The spinning of a celestial body, such as a planet, around its axis.
Down
  1. 1. A celestial body that orbits around a star, is spherical in shape, and has cleared its orbit of other debris.
  2. 2. An imaginary line around which a celestial body, such as a planet, rotates.
  3. 3. The force of attraction between two objects due to their mass.
  4. 4. The entirety of space, time, matter, and energy, including all planets, stars, galaxies, and other celestial bodies.
  5. 5. The motion of a celestial body, such as a planet, around another celestial body, such as a star.
  6. 6. The belief that the Sun is the center of the universe.