Saturn/Moon and Other Simulations

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Summary of Instances

Solar System. Simulation of the Sun, 8 planets, Pluto, and our Moon using Horizons ephemeris data for initial conditions. Need to zoom out to see Uranus and beyond. If you center on Earth (
center on
= 3) and zoom in 6 or more times, you will see the Moon orbiting the Earth.

Ephemeris Saturn's Moons. Moons from Prometheus to Phoebe are simulated using Horizons ephemeris for initial conditions. The default zoom level shows moons out to Hyperion with Iapetus transiting the corners of the window occasionally. Zoom out to see Iapetus and Phoebe better.

Moons that are coorbital (i.e., at roughly the same radius from Saturn) are shown in a common color. The most interesting example is the pair Janus/Epimetheus. Center on one of them, say Janus (
center on = 4), zoom in three levels and watch how the two do the horseshoe dance. Since a full horseshoe takes about 5 years to complete, you might want to increase the speed of the simulator: set warp = 500 or more.

The simulator also has ephemeris data for the Cassini spacecraft. It's interesting to watch it as it flies by Titan on July 7, 2006 and then again on Dec 12, 2006.

Ephemeris Epimetheus/Janus. Here only Saturn and its two horseshoeing moons are simulated using Horizons ephemeris for initial conditions.

Ephemeris Sun/Venus/Earth/Mars/2002AA29. Asteroid 2002AA29 is more or less coorbital with Earth's orbit about the Sun. Here, the Sun, Venus, Earth, and Mars are simulated using Horizons ephemeris data for initial conditions. Also shown are the Moon and asteroids 2002AA29 and Cruithne (you'll need to zoom in several levels to see the Moon). Every couple hundred years, 2002AA29 goes into a wide orbit around Earth for about 50 years before moving ahead of Earth. Increase the warp factor to observe this phenomenon. Also, by setting dt to a negative value, you can run the simulator backward in time. You will see that there was one of these 50 year "capture" events back in the middle of the first millenium AD.

Ideal Epimetheus/Janus. In this simulation, the initial conditions are given simply by putting Janus and Epimetheus in essentially circular orbits with orbital radii that differ by only 55km. In addition 10 times per year, both Saturn is hit by a large impactor chosen from a fixed direction (in the ecliptic). The hope was to see if such events could produce the small but nontrivial eccentricities of Janus/Epimetheus without destroying the horseshoe orbit.

Saturn's Inner Moons. Here, the moons from Prometheus out to Helene are simulated. They are started in circular orbits at the correct distance from Saturn. By default, the simulator is centered on Prometheus. To center on Saturn itself, select center on = 0.

Janus and 5 others. Here, we simulate Saturn, Janus, and 5 other moons identical to Janus arrayed uniformly around Saturn. Hence each moon is in an L4 position relative to the moon in front of it and in an L5 position relative to the moon behind it. This simulation shows that this configuration slips into a horseshoe-type orbit after a few hundred years.

Janus and 19 others. This is similar to the previous except that there are 20 Janus clones arrayed around Saturn. In this case, the moons were given slightly different orbital radii so that they exhibit a sort of horseshoe behavior right from the start.

Janus and 99 others. Same as before except with 100 Janus clones. Also, in this version, each moon gets a random delta-v 10 times per year. Even so, the system is quite stable.

Saturn's rings. Here are three rings of Janus clones. The system is quite stable over thousands of years. If you decrease dt to 5.0e-6 you will be able to see the motion better.