significantly over the age of the Solar System, because their orbits have remained stable following the period of giant impacts. See also Nebular hypothesis Rogue planet Tidally detached exomoon Notes References Goldreich, P., and Tremaine, S. 1979, Astrophysical Journal, 233, 857 Lin, D. N. C., and Papaloizou, J. 1979, Monthly Notices of the Royal Astronomical Society, 186, 799 Ward, W. R. 1997, Icarus, 126, 261 Tanaka, H., Takeuchi, T., and Ward, W. R. 2002, Astrophysical Journal, 565, 1257 Celestial mechanics Solar System dynamic theories