Similarly to Mercury-T, the bodies in the simulation can be static or follow predefined evolutionary models matching FGKML stars and gaseous planets. The simulations can account for several different effects:
- Tidal forces
- Rotationnal-flattening effects
- General Relativity corrections
Posidonius has a better spin integration than Mercury-T, it’s more than six times faster, it conserves the total angular momentum of the system one order of magnitude better and the spin to rotational-fattening evolution five orders of magnitude better.
It also allows a wider variety of configurations. For instance, it can simulate the evolution of evolving binary stars with planets, or an evolving Jupiter mass planet around an evolving star.
The N-body code is written in Rust, a systems programming language that runs as fast as Fortran/C, prevents segmentation faults, and guarantees thread safety. Its main characteristics are:
- Zero-cost abstractions
- Guaranteed memory safety
- Threads without data races
Rust benefits for the astronomical community were already exposed in Blanco-Cuaresma & Bolmont 2017. Posidonius also provides a Python package to easily define simulation cases in JSON format, which can be read by the Posidonius integrator and ensures reproducibility.