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Herschel's Star Gages
written by Todd Timberlake
The EJS Herschel's Star Gages Model illustrates William Herschel's methods of "star gages" by which he attempted to map out the shape of our galaxy in 1785.  Herschel's star gages (sic) relied on two important assumptions: that Herschel's telescope (his "large 20 foot" with an 18.5 inch aperture) could see to the ends of the galaxy, and that within the galactic system stars are distributed uniformly.  If the first assumption holds then the stars seen in the telescope all lie within a conical region of space with the apex at the telescope and the base at the edge of the galaxy.  If the second assumption holds then the number of stars seen in the telescope is proportional to the volume of this cone.  Since the volume of the cone is proportional to the cube of its height, the distance to the galactic edge in any direction is proportional to the cube root of the number of stars seen in that direction.

This simulation allows the user to use Herschel's method of star gages to map out the shape of an artificial "star system" for which Herschel's assumptions are valid.  One window shows the view through a telescope, with a slider to change the telescopes direction (around a single fixed axis).  Another window shows a 3D view of the star system, showing either all of the stars in the system or only those stars visible through the telescope.  A third window shows a plot of the star gages.  Plotting star gages for many different directions maps out a cross-section of the star system. An optional slider allows the user to decrease the distance to at which stars are no longer visible, and a menu allows the user to select a star system in which the stars are not distributed uniformly.  These options let the user explore how violations of Herschel's two fundamental assumptions invalidate his star gage method.

Please note that this resource requires at least version 1.5 of Java (JRE).
1 supplemental document is available
1 source code document is available
Subjects Levels Resource Types
Astronomy
- Astronomy Education
= Curricula
- Cosmic Time and Distance
= Distance Scales
- Historical Astronomy
= History of Astronomy
- Instrumentation
= Telescopes
- Milky Way
= Milky Way Structure
- Lower Undergraduate
- High School
- Instructional Material
= Interactive Simulation
Intended Users Formats Ratings
- Learners
- Educators
- General Publics
- application/java
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Access Rights:
Free access
License:
This material is released under a Creative Commons Attribution 3.0 license.
Rights Holder:
Todd Timberlake
Keywords:
Milky Way, William Herschel, field of view, galaxy, star gage, telescope
Record Cloner:
Metadata instance created May 22, 2011 by Todd Timberlake
Record Updated:
June 6, 2014 by Andreu Glasmann
Last Update
when Cataloged:
May 22, 2011
Other Collections:

shape of uniform2 distribution

Author: John Lattanzio
Posted: May 2, 2017 at 8:02PM
Source: The Open Source Physics collection

Am I doing something wrong? I get zero for counts in many directions...eg 230 to 320 degrees! There are many stars in the 3D plot but none int he telescope view. I do not have limited viewing distance turned on.
John L

» reply

Re: shape of uniform2 distribution

Author: Todd Timberlake
Posted: May 03, 2017 at 8:41AM

John, I think you may be using either the Uniform 2 or Nonuniform 2 systems from the System menu.  In that case the telescope scans in a direction that is perpendicular to the plane of the star system, so you only see stars in two different directions.  Just use the System menu to switch to Uniform 1 (or one of the other systems) and this problem should go away.  Also, note that you can click and drag in the 3D view to get a better angle of view that will help you see what is going on.
- Todd

> On May 02, 2017, John Lattanzio posted:
>
> Am I doing
> something wrong? I get zero for counts in many directions...eg
> 230 to 320 degrees! There are many stars in the 3D
> plot but none int he telescope view. I do not have
> limited viewing distance turned on.
> John L

» reply

Post a new comment on this item
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Record Link
AIP Format
T. Timberlake, Computer Program HERSCHEL'S STAR GAGES, Version 1.0 (2011), WWW Document, (http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261).
AJP/PRST-PER
T. Timberlake, Computer Program HERSCHEL'S STAR GAGES, Version 1.0 (2011), <http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261>.
APA Format
Timberlake, T. (2011). Herschel's Star Gages (Version 1.0) [Computer software]. Retrieved August 16, 2017, from http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261
Chicago Format
Timberlake, Todd. "Herschel's Star Gages." Version 1.0. http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261 (accessed 16 August 2017).
MLA Format
Timberlake, Todd. Herschel's Star Gages. Vers. 1.0. Computer software. 2011. Java (JRE) 1.5. 16 Aug. 2017 <http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261>.
BibTeX Export Format
@misc{ Author = "Todd Timberlake", Title = {Herschel's Star Gages}, Month = {May}, Year = {2011} }
Refer Export Format

%A Todd Timberlake
%T Herschel's Star Gages
%D May 22, 2011
%U http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261
%O 1.0
%O application/java

EndNote Export Format

%0 Computer Program
%A Timberlake, Todd
%D May 22, 2011
%T Herschel's Star Gages
%7 1.0
%8 May 22, 2011
%U http://www.compadre.org/Repository/document/ServeFile.cfm?ID=11214&DocID=2261


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Herschel's Star Gages:

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 Herschel's Star Gages.

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