Nightfall on Linux

Depending on the exact conditions, you may have an accretion disk of material around the central star. The second tab lets you set the type of accretion disk (that is, how it interacts with the central star), along with more physical parameters like the inner and outer diameters and the temperature.

The advanced tab allows you to set some less obvious parameters for your model, such as the eccentricity for the orbiting star and whether you also need to model the atmosphere.

Now you can click on the Compute button at the top of the window, and on most modern machines, it goes pretty quickly. Once the calculations are done, you can plot the output from the system you just modeled.

The Output menu item on the menu bar at the top gives you several options on how to display the calculated results. The first entry is PlotCurve, which draws the light curve as seen from a distant observer. Gnuplot is used to draw the actual plot of the visible amount of light that is seen.

Figure 2. Once the calculation is done, you can plot the observed light curve.

The second output option is to select ViewGeometry. This plot shows you how the stars themselves are distorted within their orbits.

Figure 3. You can plot the geometry of the stars within the binary system.

The StarView menu item presents a view of how the binary system would look from your observation point. A control box also pops up that allows you to change the inclination of the orbital plane and the phase of the orbit.

Figure 4. Selecting StarView lets you see the binary system from some distance away.

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Joey Bernard has a background in both physics and computer science. This serves him well in his day job as a computational research consultant at the University of New Brunswick. He also teaches computational physics and parallel programming.