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Kepler System Model
written by Todd Timberlake
The Kepler System model simulates Kepler's final theory of planetary motion. In this theory 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.

The Kepler System model was created using the Easy Java Simulations (EJS) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the ejs_astronomy_KeplerSystem.jar file will run the program if Java is installed.  EJS is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models.

Please note that this resource requires at least version 1.5 of Java (JRE).
1 source code document is available
Subjects Levels Resource Types
- Astronomy Education
= Curricula
- Fundamentals
= Night Sky
- Historical Astronomy
= History of Astronomy
- High School
- Middle School
- Lower Undergraduate
- Instructional Material
= Interactive Simulation
Intended Users Formats Ratings
- Educators
- Learners
- General Publics
- application/java
  • Currently 5.0/5

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Access Rights:
Free access
This material is released under a Creative Commons Attribution 3.0 license.
Rights Holder:
Todd Timberlake
EJS, Earth, Easy Java Simulations, Kepler, OSP, Open Source Physics, Sun, celestial globe, celestial sphere, elliptical, orbit, orbit
Record Cloner:
Metadata instance created January 2, 2010 by Mario Belloni
Record Updated:
June 10, 2014 by Andreu Glasmann
Last Update
when Cataloged:
January 2, 2010
Other Collections:

t/2 the actual period of the motion of the planets in years?

Author: lookang
Posted: April 6, 2010 at 5:23AM
Source: The Open Source Physics collection

just want to confirm that t/2 the actual period of the motion of the planets in years.

will be remixing it here

customize for r^2 = T^3 Kepler's #rd Law.

this is the most stunning astronomy applet! thanks Dr. Todd Timberlake

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Record Link
AIP Format
T. Timberlake, Computer Program KEPLER SYSTEM MODEL, Version 1.0 (2010), WWW Document, (
T. Timberlake, Computer Program KEPLER SYSTEM MODEL, Version 1.0 (2010), <>.
APA Format
Timberlake, T. (2010). Kepler System Model (Version 1.0) [Computer software]. Retrieved October 24, 2017, from
Chicago Format
Timberlake, Todd. "Kepler System Model." Version 1.0. (accessed 24 October 2017).
MLA Format
Timberlake, Todd. Kepler System Model. Vers. 1.0. Computer software. 2010. Java (JRE) 1.5. 24 Oct. 2017 <>.
BibTeX Export Format
@misc{ Author = "Todd Timberlake", Title = {Kepler System Model}, Month = {January}, Year = {2010} }
Refer Export Format

%A Todd Timberlake
%T Kepler System Model
%D January 2, 2010
%O 1.0
%O application/java

EndNote Export Format

%0 Computer Program
%A Timberlake, Todd
%D January 2, 2010
%T Kepler System Model
%7 1.0
%8 January 2, 2010

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The AIP Style presented is based on information from the AIP Style Manual.

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Kepler System Model:

Is Based On Easy Java Simulations Modeling and Authoring Tool

The Easy Java Simulations Modeling and Authoring Tool is needed to explore the computational model used in the Kepler System Model.

relation by Mario Belloni
Is a Teaching Guide For Physics Classroom: Kepler's Three Laws

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