Computer Program Detail Page
This record is currently in the approval process for inclusion into the PhysTEC collection. If you feel this record should be given priority you may contact the editor using our feedback form.
written by Todd Timberlake
The EJS Galileo Sunspots Model illustrates the motion and changes in appearance of sunspots as they move across the disk of the Sun. Galileo's observation of the changing appearance of sunspots around 1611 provided strong evidence that the spots were actually blemishes on the surface of the Sun, an idea that conflicted with the Aristotelean notion of the perfections of the heavens. Through these observations Galileo was able to determine the obliquity of the Sun (the angle between the Sun's equator and the Ecliptic plane) as well as the rotational period of the Sun.
The simulation shows four randomly generated sunspots, and one sunspot that has a user-defined latitude (to allow the user to examine the behavior of sunspots at various latitudes). All sunspots are oval in shape. As the spots move across the Sun their appearance changes due to foreshortening and a slight tilt as the spots approaches the limb (or edge) of the solar disk. These effects come about because the Sun's surface is spherical, not flat. So the sunspot changes it orientation relative to the viewer as it moves around on the Sun's surface.
In addition to controls that allow the user to define the latitude of one of the sunspots, this model allows the user to set the obliquity of a line representing the Sun's equator. The user can adjust the obliquity of this line until the sunspots all move parallel to the line. In this case the obliquity of the line is the actual obliquity of the Sun. In addition, the model displays the elapsed time (in days) so that the user can determine the rotational period of the Sun by measuring the time required for a sunspot to complete its motion around the Sun. (Note that the period of a sunspots motion is latitude-dependent, as it is in the real Sun.)
Please note that this resource requires at least version 1.5 of Java (JRE).
View the source code document attached to this resource
The source code zip archive contains an XML representation of the EJS Galileo Sunspots Model. Unzip this archive in your EJS workspace to compile and run… more...
download 30kb .zip
Rights: This material is released under the GNU General Public License Version 3.
Published: May 12, 2011
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.
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 Galileo Sunspots.relation by Wolfgang Christian
Know of another related resource? Login to relate this resource to it.