1. Eccentricity

2. An Ellipse is an oval shaped orbit.
What is an Ellipse?
An Ellipse is an oval shaped orbit.

3. Within the ellipse are two fixed points called foci.
For the planets in our Solar System the Sun is one of these foci.

4. The degree of flattening or “ovalness” of an ellipse.
What is eccentricity?
The degree of flattening or “ovalness” of an ellipse.

5. Where can we find the formula?

6. Ellipses (cont.) If e=0, the ellipse is a circle.
If e=1, the ellipse is a line.
As distance between foci increases, eccentricity increases.
This is a _______ relationship.
The Sun is a foci in our Solar System.

7. How do we find eccentricity?
Measure the distance between the two foci.
Divide by the length of the major axis.

8. 1. Which planet has the least distance between two foci of its elliptical orbit?
Venus
Earth
Mars
Jupiter

9. 2. Which bar graph correctly shows the orbital eccentricity of the planets in our solar system?

10. 3. The diagram below shows the elliptical orbit of a planet revolving around a star. The star and F2 are the foci of this ellipse.
What is the approximate eccentricity of this ellipse?
0.22
0.47
0.68
1.47

11. Regents Questions

12. Free Write: What you know about eccentricity of ellipses?
Take out a piece of loose leaf and fold it in half. Write your response on one half.
You may use the diagram, your notes, and the E.S.R.T. to help you write your details.
Keep writing until time is announced to stop

13. Free Write: How did Kepler’s Laws of Planetary Motion help to explain and refine our knowledge of the planets’ revolution around the Sun?
Write your response on the unused half of paper.
You may use the diagram and the E.S.R.T. to help you write your details.
This is an individual task
Keep writing until time is announced to stop