N-body Code for Planet Formation

N-Body codes calculate orbits of planets around a star

Accurate gravity field
Perturbations due to close passes
Objects merge when they collide

N-Body codes have several advantages

Calculate evolution of large planets accurately
Can treat gas accretion and migration more accurately
Derive orbits of large planets
Derive final planet masses

N-Body codes also have some disadvantages

Cannot calculate evolution of planetesimals
(too many orbits to follow)
No interaction with leftover planetesimals
No predictions for dust production

Our approach: Encke method

Inertial coordinate frame follows Keplerian orbit
Friends-of-friends for nearest neighbors
Hierarchical treatment of timesteps
Force-evaluations calculated directly
Treecode backup for large numbers of particles
Input drag from interactions with gas & small bodies
Input accretion from planetesimal swarm
Accuracy is machine precision for orbits
O(N2) for force-solver

Code has been extensively tested

Code reproduces previous calculations

We used the n-body code to calculate the evolution of icy planets after a stellar encounter.
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