M. Fabbrichesi , SISSA

In this lesson the professor continues with the solution for the motion in a central field by obtaining the equation for the orbits. Then he focus in the solutions for the **Kepler problem** were he calculates the orbits in terms of trigonometric functions, he disciuses then all the posibles orbits depending on the energy of the particle confirmig the reasoning done in the past lesson. In the secound part of the lesson he discusses the motion of the planets as seeing from the earth and calculates the **orbital eccentricity**.

Definition of the <span id="eow-title" title="Orbit Eccentricity" dir="ltr">Orbit Eccentricity, the solar system case.</span>

Binary star orbits (mass ratio = 2, eccentricity = 0.4) As an example of the solution of the two body problem in a central field this video shows the binary star orbits. The center of mass is shown as the 'x'. Here the mass ratio of the stars is 2 and the eccentricity is 0.4. Other mass ratios and eccentricities available on this channel.