Kepler System 1.0
A free software that allows you to view the planetary motion in real-time
In Kepler System the planets orbit in ellipses with Sun at one focus (Kepler's First law). These elliptical orbits are not necessarily all in the same plane.
A line from Sun to the planet sweeps out equal areas in equal times (Kepler's Second law). The square a planet's period is directly proportional to the cube of the semimajor axis of its elliptical orbit (Kepler's Third law).
The simulation shows Earth's orbit around Sun, as well as the orbit of one other planet. The user can choose to show one of the five visible planets (Mercury, Venus, Mars, Jupiter, or Saturn), or a fictitious planet.
The top window shows the orbits of the planets around Sun. The view can be changed by clicking and dragging in the window and a zoom slider is provided to zoom in or out.
The bottom window shows the view of Sun and planet against the background stars as seen from Earth.
NOTE: Kepler System is licensed and distributed under the terms of the Creative Commons Attribution 3.0 license.