1. Eccentricity

2. 4/20/17
Eccentricity
Aim:
I can understand eccentricity.
Do Now:
What do you think an ellipse is? Does every planet or moon have a circular orbit?
Homework:
- Exit Project due May 12th
Work on your data analysis

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

4. Kepler’s First Law
1. The Law of Orbits: All planets move in elliptical orbits, with the sun at one focus.

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

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

7. 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.
The Sun is a foci in our Solar System.

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

9. 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