Some orbits more popular than others in solar systemsComputer simulations have revealed a plausible explanation for a phenomenon that has puzzled astronomers: Rather than occupying orbits at regular distances from a star, giant gas planets similar to Jupiter and Saturn appear to prefer to occupy certain regions in mature solar systems while staying clear of others.
Source: Some orbits more popular than others in solar systems (http://www.sciencedaily.com/releases/2012/03/120319111601.htm)