Published online by Cambridge University Press: 22 February 2018
This review states and defends seven conclusions on the origin of comets and the evolution of their orbits:
1. There is a N-½ law of survival of comets against ejection on hyperbolic orbits, where N is the number of perihelion passages.
2. The short-period comets are not created by single close encounters of near-parabolic comets with Jupiter.
3. Observable long-period comets do not evolve into observable short-period comets.
4. Unobservable long-period comets with perihelia near Jupiter can evolve into observable short-period comets.
5. Long-period comets cannot have been formed or created within the planetary region of the solar system. (This conclusion is somewhat qualified because of possible effects of stellar perturbations. )
6. It is possible that some of ths short-period comets could have been formed inside the orbit of Neptune, but it is certain that others have the same distant source as the long-period comets.
7. The circularly-restricted 3-body problem, and its associated Jacobi integral, are not valid approximations to use in studying origin and evolution of comets.