It can be demonstrated that for objects in orbit around a star (or planet) the orbital period squared
should be proportional to the cube of the orbit's semimajor axis. This is because the gravitational
force is inversely proportional to the distance squared.
To show this law in action, we ploted the values for the case of the planets in our solar system.
Indeed, they fall on a straight line as expected.
Notice that to better accomodate all the different values we are using a log-log scale.
A.U. is an astronomical unit, equal to 1.5 x 108 km.