The software lies within Theming Tools, more precisely Screensavers.
From the developer:
TriVectus Planets is a screen saver that displays and animates various planetary systems. In addition, you'll see exploding planets, asteroid swarms, rouge asteroids, and nuclear war, among other things. Watch a planet's moon spiral into space after the planet explodes, or see how a rouge asteroid wrecks havoc with its gravitational field as it passes through the system.
You may want to check out more Mac applications, such as Fishing Planet, Planets -- Live Wallpaper or Blue Planet, which might be similar to TriVectus Planets.
Simulation