Vocab 28.1

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Across
  1. 3. first person to observe the sky using a telescope
  2. 6. discovered gravity
  3. 8. the point in the orbit of a planet at which is closest to the sun
  4. 10. the shape of a planet's elliptical orbit.
  5. 11. unit a distance in space
  6. 12. formulated a model of the universe
Down
  1. 1. objects ranging from km to hundreds of km
  2. 2. motion the backward movement of a planet
  3. 4. the point in the orbit of a planet at which is the furthest from the sun
  4. 5. one of two fixed points used to define an ellipse
  5. 7. discovered shapes of planetary orbits
  6. 9. an oval shape centered on two points