- Kepler's first law
Orbits are ellipses within which the Sun is one of the focuses (animation 1 of an ellipse).
- Kepler's second law
The "area law" : the velocity along the orbit is such that the area swept from the Sun is constant. When the planet is closer to the Sun, it goes faster. (animation 2 of an ellipse).
- Kepler's third law
The period P of revolution around the Sun increases with the semimajor axis*, D, and
is constant for all the planets of the Solar System.
* : the semimajor axis is the mean distance from the Sun.
If P is in terrestrial years and D in astronomical units, the constant is equal to 1.
For a planet at 5 AU,