  In the nucleated instability picture of gas giant formation, the final stage
is the rapid accretion of a massive gas envelope by a solid core, bringing
about a tenfold or more increase in mass. This tends to trigger the scattering
of any nearby bodies, including other would-be giant planet cores; it has been
shown in past work that the typical outcome is an outer planetary system very
similar to our own. Here, we show that the gravitational scattering
accompanying the formation of gas giant planets can also produce, in some
cases, outer planets with semimajor axes much larger than those in the Solar
System, and eccentricities which remain high for tens of millions of years.
Rings, gaps and asymmetries detected in a number of circumstellar dust disks,
which hint at the presence of embedded planets at stellocentric distances far
beyond where planet formation is expected to occur, may be connected to such a
scenario.
