Fig2_2 Kepler third

Fig2_2 Kepler third

Fig. 2.2 . The orbital periods of the planets in years are plotted against the semi-major axes of their elliptical orbits in astronomical units abbreviated AU, using a logarithmic scale. The straight line that connects the points has a slope of 3/2, thereby verifying Keplerís third law that states that the square of the orbital periods increase with the cubes of the planetary distances. The German astronomer Johannes Kepler (1571-1630) published this third law in 1619. This type of relation applies to any set of bodies in elliptical orbits, including Jupiterís four largest satellites shown in the inset, with a vertical axis in units of days and a horizontal axis that gives the distance from Jupiter in AU units.

Copyright 2010, Professor Kenneth R. Lang, Tufts University