Home
Map
Glossary
Contact
Links
Observatoire de Paris
ExoplanetsCoRoTCourseToolsDatabase
<-   Kepler's laws   ->
Java 1.1 is required to display this animation
Illustration of Kepler's second law.
Copyright : ASM
  • 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
    P^2/D^3
    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,
    P^2=5^3=125
    then P=racine(125)=11.2 years