A certain comet orbits the sun in an elliptical orbit of eccentricity equal to 1/2. In this case, the semimajor axis, 'a', is exactly equal to twice 'c', the distance from the sun to the center of the ellipse, as shown below. The speed of the comet when it is  closest to the sun (the perihelion) compared to the speed of the comet when it is farthest from the sun (the aphelion) is