Spiral Nebula Rotation
written by Todd Timberlake
The EJS Spiral Nebula Rotation model illustrates a simplified version of Adrian van Maanen's method for measuring the rotations (or internal motions) of spiral nebulae. Van Maanen used a device called a "blink stereocomparator" that allowed him to rapidly switch between viewing one image of a spiral nebula and another image of the same nebula taken at a later date. After aligning the foreground stars (which were not part of the nebula) in the two images, van Maanen made measurements of the displacements of various points in the nebula from one image to the other.
The simulation provides two images of the spiral nebula Messier 101, derived from a Hubble Space Telescope image. The user can "blink" back and forth between these two images. Foreground "stars" (red dots) have been superimposed on the two images. The user must first align the foreground stars by rotating the second image of the nebula. Then the displacements and distances from center of various points in the nebula can be measured using the draggable arrows in the simulation, and these values can be used to determine the angle by which the nebula has rotated in the time interval between the two images.
It should be emphasized that the rotation effect illustrated in this simulation is NOT REAL. Although spiral galaxies do rotate, the angle by which they rotate during a human lifetime is so small as to be undetectable. The purpose of this simulation is simply to illustrate van Maanen's method, because van Maanen's (spurious) results were historically important in that they led several astronomers to reject the idea that spiral nebulae are independent galaxies (at least for a while).
Please note that this resource requires at least version 1.5 of Java (JRE).
1 source code document is available
The source code zip archive contains an XML representation of the EJS Spiral Nebula Rotation Model. Unzip this archive in your EJS workspace to compile and run this model using EJS.
download 1151kb .zip
Published: May 12, 2011
Rights: This material is released under the GNU General Public License Version 3.
ComPADRE is beta testing Citation Styles!
Disclaimer: ComPADRE offers citation styles as a guide only. We cannot offer interpretations about citations as this is an automated procedure. Please refer to the style manuals in the Citation Source Information area for clarifications.
Citation Source Information
The APA Style presented is based on information from APA Style.org: Electronic References.
The Chicago Style presented is based on information from Examples of Chicago-Style Documentation.
The MLA Style presented is based on information from the MLA FAQ.
Spiral Nebula 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 Spiral Nebula Rotation.relation by Wolfgang Christian
Know of another related resource? Login to relate this resource to it.