A popular solution to this dilemma is to assume that the Solar System was initially more compact and that the outer planets migrated to their current positions via the exchange of momentum between the planets and planetesimals originating from an outer disk.
A popular solution to this dilemma is to assume that the Solar System was initially more compact and that the outer planets migrated to their current positions. This process is driven by the exchange of angular momentum between the planets and planetesimals originating from an outer disk.