APS Excellence in Physics Education Award
November 2019

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Science SPORE Prize
November 2011

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The Open Source Physics Project is supported by NSF DUE-0442581.

Computer Program Detail Page

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Astronomical Parallax 3D
written by Todd Timberlake
This Astronomical Parallax 3D Model illustrates the phenomenon of annual stellar parallax in astronomy. Parallax is the apparent displacement of an object relative to the background that is caused by the motion of the observer (rather than the motion of the object itself, or of the background). This simulation illustrates the parallax of an object in space that results from the Earth's annual orbital motion.

The Space View window shows the Earth (blue point) orbiting the Sun (organe point). The white point represents a stationary star. The open white circle shows the location of the object on the celestial sphere as seen from the Sun.  The magenta point shows the location of the star on the celestial sphere as seen by an observer on the orbiting Earth. Various options allow the user to display the line of sight from Earth through the star, the line from the Sun through the star, cardinal direction arrows, the trace of the star's apparent motion, the trace of Earth's orbit, and the planes and axes of the celestial equator and ecliptic. Controls allow the user to adjust the distance to the star as well as its celestial coordinates (as seen from the Sun). Another menu allows the user to select a particular day (equinox or solstice) of the year.

The Sky View window shows the apparent location of the star on the sky as seen by an Earth observer. The "true location" (the location as seen from the Sun) is shown as an open white circle, while the apparent location is shown as a magenta disk.

Note that some features have been simplified or exaggerated. The Earth's orbit is treated as a circle. The distances to the "star" are vastly smaller than the distance to any real star (at the distance to the nearest real star the annual parallax would be imperceptible in this simulation). The size of the Earth, sun, and star are exaggerated so as to make them visible on the scale of the simulation.

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
- Cosmic Time and Distance
= Parallax
- Historical Astronomy
= History of Astronomy
- Solar System
= Earth
- Lower Undergraduate
- High School
- Instructional Material
= Demonstration
Intended Users Formats Ratings
- Learners
- Educators
- General Publics
- application/java
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Access Rights:
Free access
This material is released under a GNU General Public License Version 3 license.
EJS, Easy Java Simulations, OSP, Open Source Physics, apparent position, orbit, parallax, rotation
Record Creator:
Metadata instance created May 16, 2011 by Todd Timberlake
Record Updated:
January 25, 2023 by Lyle Barbato
Last Update
when Cataloged:
May 16, 2011
Other Collections:

ComPADRE is beta testing Citation Styles!

Record Link
AIP Format
T. Timberlake, Computer Program ASTRONOMICAL PARALLAX 3D, Version 1.0 (2011), WWW Document, (https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246).
T. Timberlake, Computer Program ASTRONOMICAL PARALLAX 3D, Version 1.0 (2011), <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246>.
APA Format
Timberlake, T. (2011). Astronomical Parallax 3D (Version 1.0) [Computer software]. Retrieved May 22, 2024, from https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246
Chicago Format
Timberlake, Todd. "Astronomical Parallax 3D." Version 1.0. https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246 (accessed 22 May 2024).
MLA Format
Timberlake, Todd. Astronomical Parallax 3D. Vers. 1.0. Computer software. 2011. Java (JRE) 1.5. 22 May 2024 <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246>.
BibTeX Export Format
@misc{ Author = "Todd Timberlake", Title = {Astronomical Parallax 3D}, Month = {May}, Year = {2011} }
Refer Export Format

%A Todd Timberlake %T Astronomical Parallax 3D %D May 16, 2011 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246 %O 1.0 %O application/java

EndNote Export Format

%0 Computer Program %A Timberlake, Todd %D May 16, 2011 %T Astronomical Parallax 3D %7 1.0 %8 May 16, 2011 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11202&DocID=2246

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Astronomical Parallax 3D:

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 Astronomical Parallax 3D.

relation by Wolfgang Christian

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