(1) 150 million kilometers (2) 228 million kilometers The diagram below shows the orbital paths of Earth, Mars, Jupiter, and a comet named Wild 2. What is the approximate distance between the Sun and Wild 2 when this comet is closest to the Sun? (1) 150 million kilometers (2) 228 million kilometers (3) 778 million kilometers (4) 820 million kilometers

Whew!

Are all elliptical orbits the same?

If the foci are far apart, the orbit is very elliptical. The closer the foci get to each other the more the orbit becomes a circle. f1 f2 f1 f2 f1 f2

Which ellipse is most eccentric? If the foci are far apart, the orbit is very elliptical. The closer the foci get to each other the more the orbit becomes a circle. We measure the shape of the ellipse by its eccentricity. Rounder = less eccentric Most eccentric f1 f2 Which ellipse is most eccentric? f1 f2 Least eccentric f1 f2

Increasing eccentricity f Increasing eccentricity f1 f2 f1 f2 f1 f2

When is gravity strongest. When is velocity slowest When is gravity strongest? When is velocity slowest? When does sun appear largest? When is it summertime in New York?

Which statement concerning the diagram is probably true? The diagram below represents the path of the Earth’s orbit around the sun compared to the path of the orbit of a comet around the sun. Which statement concerning the diagram is probably true? (1) A comet has a less eccentric orbit and a shorter period of revolution than the Earth. (2) A comet has a more eccentric orbit and a shorter period of revolution than the Earth. (3) A comet has a less eccentric orbit and a longer period of revolution than the Earth. (4) A comet has a more eccentric orbit and a longer period of revolution than the Earth.