P2 = a3
| 2 = | 3 = |
| Period P (years): | 0.1250 |
| Semi-major Axis a (AU): | 0.140 |
Kepler's third law states that the period (P) of an object orbiting the Sun is equal to the semi-major axis (a) cubed. This is only an equality when "P" is measured in years and "a" in astronomical units. The following table shows that as the size of the orbit increases the orbital period increases as well. Note that P grows more rapidly than a does..
| Object | P (years) | a (AU) |
|---|---|---|
| Earth | 1 | 1 |
| Mars | 1.9 | 1.5 |
| Asteroid | 8 | 4 |
| Jupiter | 11.9 | 5.2 |
| Neptune | 165 | 30 |