Table 4-3: A Demonstration of Kepler’s Third Law (P2 = a3)
| Planet | Sidereal period P (years) | Semimajor axis a (AU) | P2 | a3 |
|---|
| Mercury | 0.24 | 0.39 | 0.06 | 0.06 |
| Venus | 0.61 | 0.72 | 0.37 | 0.37 |
| Earth | 1.00 | 1.00 | 1.00 | 1.00 |
| Mars | 1.88 | 1.52 | 3.53 | 3.51 |
| Jupiter | 11.86 | 5.20 | 140.7 | 140.6 |
| Saturn | 29.46 | 9.55 | 867.9 | 871.0 |
| Uranus | 84.10 | 19.19 | 7,072 | 7,067 |
| Neptune | 164.86 | 30.07 | 27,180 | 27,190 |
| Kepler’s third law states that P2 = a3 for each of the planets. The last two columns of this table demonstrate that this relationship holds true to a very high level of accuracy. |