This simulator models the motions of two stars in orbit around each other. When such a system is aligned properly the stars will eclipse one another, causing a change in brightness (as seen from earth) that allows astronomers to determine the properties of the stars.
The upper left panel shows the binary system visualization. If the lock on perspective from earth checkbox is selected (found in the lower left corner) the system is shown as it would be seen from earth with a sufficiently powerful telescope. If the perspective is unlocked one can drag the visualization around, and a red arrow is shown indicating the direction to the earth.
In practice eclipsing binary stars are so close together that astronomers see just a single combined 'star'. The plot in the upper right shows the combined brightness of the system. Dips in the lightcurve correspond to the eclipses as seen from earth.
The panel in the lower right controls the properties of the stars. Note that as you adjust one slider the range of the other sliders may change (indicated by the dark shading) to prevent the stars from physically overlapping. The longitude and inclination properties in the left panel control the orientation of the system with respect to earth.
You can also load presets from the presets drop-down box. With some presets observed data will be shown in the lightcurve panel. This data comes from the CALEB catalog located here .