Following creation of a CONDOR PC mini-cluster for the Observatory, early in 2004, it became possible to pursue new projects involving very large-scale numerical simulations that had previously been beyond the reach of a single work-station. Apostolos Christou completed large -body simulations with CONDOR using the MERCURY -body integration package to investigate a contemporary issue in solar system dynamics.
Groups of newly discovered Jovian irregular satellites appear to be less compact than theory predicts. In other words, the dispersion of orbits within each group is larger than hydrocode simulations of collisional fragmentation of one or more parent bodies would suggest. Attention has focused in particular on a group containing the large irregular satellite Himalia, with the result that in treating Himalia as a body with mass, rather than assuming it is a massless particle as in previous work, the group disperses with time and can reproduce the picture we see today.
Equally interesting is the discovery that gravitational resonances can operate between irregular satellites, a hitherto unexpected mechanism that also modifies the orbits with time. These results were presented at the 2004 ASGI/IoP meeting in Armagh in April 2004, and at the 35th Division of Dynamical Astronomy meeting of the American Astronomical Society in Cannes, France (also in April 2004). A paper on the subject has been accepted for publication in Icarus.