Orbital structure of the Solar System (left) and the HR 8799 system (right). The inner belts are represented in red and the outer belts in blue. Planet masses are indicated by the size of the dots; each plot has a separate log scale. We note that the orbital eccentricities of the giant planets in the HR 8799 system are several times larger than the eccentricities of the Solar System giants, which lead to more impacts between planets and small bodies.