The Leavitt's Cepheid Variables Model allows the user to explore the relationship between period and apparent magnitude for Cepheid variables in the Magellanic Clouds, first discovered by Henrietta Levitt in 1912.  The main window displays a photographic negative of a star field.  When the simulation is played, the main window displays an animated sequence of photo negatives taken at 1 day intervals.  Each star field contains one Cepheid variable star, which can be identified by its changing size in the photographic negative.

A tool for measuring apparent magnitude is provided, and a plot of the light curve (modulo a test period) can be displayed.  These tools let the user measure the median apparent magnitude and period of the Cepheid variable. Resetting the simulation generates a new star field, so the user can measure many Cepheid variables and discover the relationship between period and luminosity for these stars, originally found by Leavitt for the star in the Small Magellanic Cloud.

The Leavitt Cepheid Variables Model was created using the Easy Java Simulations (EJS) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the ejs_LeavittCepheidVariables.jar file will run the program if Java is installed.

Please note that this resource requires at least version 1.5 of Java (JRE).