1. The suns ___ keeps the planets in our solar system in orbit around the sun. 2. Comets are examples of bodies that complete parabolic or ___ orbits. 3. The orbits of all planets in the solar system are slightly elliptical with the exception of . 4. Kepler’s laws describe how objects move through space; ___ laws describe why objects move in this way. 5. Describe the differences between a geocentric model and heliocentric model. What model is the current Sun-Earth-Moon system based on?