The simple animation below shows this change in orbital speed. You can alter the orbit shape by clicking on the buttons at the top of the blue region. The buttons are labeled with the orbital "eccentricity," a measure of the ellipticity of the orbit. Eccentricity = 0.0 corresponds to a circle. The larger the eccentricity, the more elongated the orbit. An eccentricity =1.0 corresponds to an open orbit.
To stop the animation, click on the blue area. It takes a moment or two to stop running.
Choose an eccentricity (E) for the orbit by clicking a button below