1. Johannas Kepler Johannas Kepler Planetary Orbital Laws Planetary Orbital Laws

2. Kepler’s First Law The orbit of the planets are ellipses, with the sun at one focus of the ellipse. The orbit of the planets are ellipses, with the sun at one focus of the ellipse.ellipses

3. Ellipses and Eccentricity Eccentricity The amount of flattening of the ellipse is termed the eccentricity. The amount of flattening of the ellipse is termed the eccentricity. Circle = 0 Circle = 0 Straight Line = 1 Straight Line = 1

4. Ellipses The sun is not at the center of the ellipse. The sun is not at the center of the ellipse.sun There is nothing at the other focus. There is nothing at the other focus.

5. Kepler’s Second Law Second LawSecond Law The line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse. The line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse.out equal out equal Good Example Good Example Good Example Good Example Perihelion = Point closest to Sun (fastest) Perihelion = Point closest to Sun (fastest) Aphelion = Point farthest from Sun (Slowest) Aphelion = Point farthest from Sun (Slowest)

6. Astronomical Distances An Astronomical Unit (AU) is the average distance between Earth and the Sun. An Astronomical Unit (AU) is the average distance between Earth and the Sun. Used when measuring distances to other solar system objects. Used when measuring distances to other solar system objects. A Light year is the distance it takes light to travel in 1 year. A Light year is the distance it takes light to travel in 1 year.Light year Light year Used to measure distances to other stars and galaxies. Used to measure distances to other stars and galaxies.

7. Kepler’s Third Law Third LawThird Law The closer the object is to the Sun the faster its period of revolution. The closer the object is to the Sun the faster its period of revolution. Example: Example: Earth & Mars Orbit Earth & Mars Orbit