N-body simulation

Initial Conditions of an N-body simulation

The following image shows the initial conditions of an N-body simulation involving 2500 particles, starting from a ``Plummer'' model, constructed using the Starlab software package.

After 120 dynamical times, the core has shrunk somewhat, and the system looks like:

After 248 dynamical times, the core is at the point of collapse:

The first close binaries form just after this time. After this point, the cluster enters a period of overall expansion, driven by binary heating in the core. The core oscillates in response to alternating periods of binary formation, heating and ejection. By 280 dynamical times, the core radius has expanded to about 10 times its minimum value:

At the end of the simulation, at 330 dynamical times, the system contains 5 close binaries (with energies in the 100-200 kT range):

The time variation of the cluster's core radius is shown below.

For more on N-body simulations, see Star Cluster Evolution with Primordial Binaries: III. Effect of a Galactic Tidal Field, S.L.W. McMillan and P. Hut, Astrophysical Journal, 427, 793 (1994), and references therein.