Illustration of Kepler’s laws with two planetary orbits.
- The orbits are ellipses, with foci F 1 and F 2 for Planet 1, and F 1 and F 3 for Planet 2. The Sun is at F 1.
- The shaded areas A 1 and A 2 are equal, and are swept out in equal times by Planet 1’s orbit.
- The ratio of Planet 1’s orbit time to Planet 2’s is (a 1/a 2) 3/2 {\textstyle ({a_{1}}/{a_{2}})
(echo:: @ ᯤ)