Nightfall on Linux

The RocheSlicer menu item provides a way to visualize just how distorted the stars become. A control box also pops up that lets you select various slices through the star system.

Figure 5. The RocheSlicer lets you investigate the distortions in the stars of your binary system.

The last menu item is the DataSheet option. This option pops up a new window with a text description of the results of all of the calculations that were made.

Figure 6. The DataSheet gives you the detailed numerical results of your simulation.

One of the keys in science is being able to reproduce your results, both experimental and computational. With this in mind, you can save the model you just ran and load it again later. These models are saved as configurations by clicking the menu item File→Save Configuration. You can load previous models by clicking the menu item File→Open config file. If you compiled and installed Nightfall using the instructions above, you will have a number of example configurations available that you can play with as well.

Nightfall is not only useful in determining what a given binary star system would look like, but you also can feed in your own observational data and calculate a best-fit model to those observations. You can load your observational data by clicking the menu item File→Open data file. Again, if you compiled and installed Nightfall following the instructions above, you will have several sample data files that you can load. You probably should click on the menu item File→Clear memory first. Once the data is loaded, select the Data Fitting tab in the main window. You then need to select the Mass and/or Separation buttons as parameters for the fitting. Then, select the FIT with tolerance button, using the tolerance you enter within the text box. You also can choose whether to use simulated annealing or Monte Carlo methods. You may want to do some research to see how active astronomers use these parameters to find best-fit models.

The last thing to notice is that almost everything you can do with the GUI is also doable with command-line options. This means you can generate many different models with different sets of parameters and generate the relevant plots and output data automatically. This way, you can farm out the work to some cluster of machines (but that's moving into the realm of "professional" astronomy and beyond the scope of this article).

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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.