Functions:
The choice menu at bottom right gives a selection of doubles with accurately
known orbits.
'Start' and 'Stop' begin and pause the simulation.
'Reset' return the simulation to time=0.
'Orbits' highlights the elliptical orbits followed by the components of the
double.
'Grid' shows a calibrated length scale (in [AU]), centered on the stars'
center of mass.
'ZoomIn' and 'ZoomOut' change the scale of the display
by a factor of two. 'Labels'
attaches text labels to the stars.
The scrollbars show the double's parameters: massA and massB (in [solar masses]), the semimajor axis (in [AU]) and eccentricity of the orbits.
The screen shows the distance from Earth to the chosen double (in parsecs, [pc]), the
orbital period (in [yrs]),
the
elapsed time (in [yrs]) and the current separation between the two stars (in [AU]).
Designing Your Own: You can use the scrollbars to design your own double star system and see how properties such as the geometry and period change. (The choice window will black out, to indicate that you are no longer simulating a double from its list.)
The Simulation:
The stars are started at greatest separation (apastron) at time=0 and their
motion
is followed through simple elliptical trajectories using a fixed time step,
with orbit parameters taken either from stored data (for a real double)
or from the scrollbars.