We are now in a position to do some performance analysis.
Bit of a tidy up and plot everything relative to the sun.

~/Dropbox/Private/Leapfrog $ ghc -O2 -rtsopts --make Symplectic.lhs -threaded -main-is Symplectic -fforce-recomp
[1 of 1] Compiling Symplectic       ( Symplectic.lhs, Symplectic.o )
Linking Symplectic ...

~/Dropbox/Private/Leapfrog $ ./Symplectic +RTS -s -N1 -A60M

  Total   time    5.04s  (  6.34s elapsed)

~/Dropbox/Private/Leapfrog $ ./Symplectic +RTS -s -N2 -A60M

  Total   time    5.38s  (  5.21s elapsed)

Not much of a speedup from parallelism though.