Use the fact that the orbit of a planet about the Sun is an ellipse, Mean distance with the Sun at one focus. The aphelion of a planet is its greatest distance from the Sun, and the perihelion is its shortest distance. Aphelion Perihelion The mean distance of a planet from the Sun is the length of the Major semimajor axis of the elliptical orbit. See the illustration. The O axis mean distance of planet A from the Sun is 75 million miles. If the Center Sun aphelion of planet A is 77.5 million miles, what is the perihelion? Write an equation for the orbit of planet A around the Sun The perihelion is 72.5 million miles. (Type an integer or a decimal.) The equation for the orbit of planet A around the Sun is 1 (Use integers or decimals for any numbers in the expression.)