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

Computer Program Detail Page

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Differential Galactic Rotation
written by Todd Timberlake
The EJS Differential Galactic Rotation Model illustrates the model of galactic rotation proposed by Jan Oort in 1927.  In Oort's model most of the mass of the galaxy is concentrated at the center.  Stars move in circular orbits around the center, with orbital speeds that are inversely proportional to the square root of their distance from the center.  Oort realized that this model produced a specific pattern of radial velocities in the stars near the sun, and that this pattern matched the observational data fairly well.  The simulation is intended to illustrate both Oort's model and the resulting pattern in the radial velocities.  The simulation can also depict the so-called "high-velocity" stars, which are stars that have very low orbital speeds (treated as zero in the simulation) around the galactic center and therefore have high speeds relative to the sun.

One window depicts stars (including the sun) orbiting counterclockwise around the galactic center as seen from above the galactic North pole.  The velocity vectors of the stars can be displayed, and stars near the sun can be highlighted.  Another window shows the highlighted stars (and, optionally, the high-velocity stars) in the region near the sun.  The radial velocity and relative velocity vectors for these stars can be displayed.  Finally, a plot of radial velocity versus galactic longitude (using either the modern longitude system in which the galactic center is at longitude 0, or the pre-1958 system with the galactic center at longitude 325 degrees) can be shown.  The plot can display data for the highlighted stars, the high-velocity stars, and two sets of Cepheid variables studied by Alfred Joy in 1939.  Using the Cepheid period-luminosity relation Joy found distances to these stars that fit with the distances derived from Oort's rotational model, provided that the apparent magnitudes of the stars were corrected for interstellar absorption.

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
- Historical Astronomy
= History of Astronomy
- Milky Way
= Galactic Center
= Milky Way Structure
- Lower Undergraduate
- High School
- Upper Undergraduate
- Instructional Material
= Interactive Simulation
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.
Rights Holder:
Todd Timberlake
Jan Oort, Milky Way, galaxy, high-velocity stars, radial velocity, rotation
Record Cloner:
Metadata instance created May 19, 2011 by Todd Timberlake
Record Updated:
November 11, 2021 by Lyle Barbato
Last Update
when Cataloged:
May 10, 2011
Other Collections:

ComPADRE is beta testing Citation Styles!

Record Link
AIP Format
T. Timberlake, Computer Program DIFFERENTIAL GALACTIC ROTATION, Version 1.0 (2011), WWW Document, (https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259).
T. Timberlake, Computer Program DIFFERENTIAL GALACTIC ROTATION, Version 1.0 (2011), <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259>.
APA Format
Timberlake, T. (2011). Differential Galactic Rotation (Version 1.0) [Computer software]. Retrieved July 17, 2024, from https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259
Chicago Format
Timberlake, Todd. "Differential Galactic Rotation." Version 1.0. https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259 (accessed 17 July 2024).
MLA Format
Timberlake, Todd. Differential Galactic Rotation. Vers. 1.0. Computer software. 2011. Java (JRE) 1.5. 17 July 2024 <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259>.
BibTeX Export Format
@misc{ Author = "Todd Timberlake", Title = {Differential Galactic Rotation}, Month = {May}, Year = {2011} }
Refer Export Format

%A Todd Timberlake %T Differential Galactic Rotation %D May 10, 2011 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259 %O 1.0 %O application/java

EndNote Export Format

%0 Computer Program %A Timberlake, Todd %D May 10, 2011 %T Differential Galactic Rotation %7 1.0 %8 May 10, 2011 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11212&DocID=2259

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Differential Galactic Rotation:

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 Differential Galactic Rotation.

relation by Wolfgang Christian

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