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Computer Program Detail Page

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Two Body Orbits Model
written by Wolfgang Christian
The Two Body Orbits model for teachers shows the motion of two objects (binary star or moon-planet system) interacting via Newton's law of universal gravitation.  It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter).  An optional 3D view shows the celestial sphere and and the orbital plane (ecliptic).  Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.
An important feature of the ready-to-run Two Body Orbits simulation is that it can be customized by teachers to meet various learning objectives. The teacher sets the ratio of the two masses, their initial positions and velocities, and various visualization and scale parameters.  Documentation, such as an exercise or lesson, can be added to the simulation by entering a filename into the Customization dialog.  Selecting the "student" checkbox creates a ready-to-run package with the new configuration without the Customization dialog.

The Two Body Orbits model was created using the Easy Java Simulations (EJS) modeling tool.  It is distributed as a ready-to-run Java archive.  Double clicking the ejs_mech_orbits_TwoBodyOrbits.jar file will run the program if Java is installed.  EJS is a part of the Open Source Physics Project and is available in the OSP Collection.

Please note that this resource requires at least version 1.6 of Java.
1 supplemental document is available
1 source code document is available
Subjects Levels Resource Types
Classical Mechanics
- Gravity
= Orbits
= Universal Gravitation
- Motion in Two Dimensions
= Center of Mass
= Central Forces
General Physics
- Computational Physics
- Upper Undergraduate
- Lower Undergraduate
- Instructional Material
= Interactive Simulation
Intended Users Formats Ratings
- Learners
- Educators
- application/java
  • Currently 5.0/5

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Access Rights:
Free access
This material is released under a GNU General Public License Version 3 license.
Rights Holder:
Wolfgang Christian
Record Cloner:
Metadata instance created July 13, 2012 by Wolfgang Christian
Record Updated:
June 24, 2015 by Wolfgang Christian
Last Update
when Cataloged:
July 13, 2012
Other Collections:

AAAS Benchmark Alignments (2008 Version)

4. The Physical Setting

4A. The Universe
  • 3-5: 4A/E3. Planets change their positions against the background of stars.
  • 3-5: 4A/E4. The earth is one of several planets that orbit the sun, and the moon orbits around the earth.
4G. Forces of Nature
  • 9-12: 4G/H1. Gravitational force is an attraction between masses. The strength of the force is proportional to the masses and weakens rapidly with increasing distance between them.

NSES Content Standards

Con.B: Physical Science
  • 5-8: Motion & Forces
  • 9-12: Motions & Forces
Con.D: Earth & Space Science
  • K-4: Objects in the Sky
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Record Link
AIP Format
W. Christian, Computer Program TWO BODY ORBITS MODEL, Version 1.0 (2012), WWW Document, (
W. Christian, Computer Program TWO BODY ORBITS MODEL, Version 1.0 (2012), <>.
APA Format
Christian, W. (2012). Two Body Orbits Model (Version 1.0) [Computer software]. Retrieved May 18, 2024, from
Chicago Format
Christian, Wolfgang. "Two Body Orbits Model." Version 1.0. (accessed 18 May 2024).
MLA Format
Christian, Wolfgang. Two Body Orbits Model. Vers. 1.0. Computer software. 2012. Java 1.6. 18 May 2024 <>.
BibTeX Export Format
@misc{ Author = "Wolfgang Christian", Title = {Two Body Orbits Model}, Month = {July}, Year = {2012} }
Refer Export Format

%A Wolfgang Christian %T Two Body Orbits Model %D July 13, 2012 %U %O 1.0 %O application/java

EndNote Export Format

%0 Computer Program %A Christian, Wolfgang %D July 13, 2012 %T Two Body Orbits Model %7 1.0 %8 July 13, 2012 %U

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Citation Source Information

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

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Two Body Orbits 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 Two Body Orbits Model.

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