The Oort cloud is a loose collection of billions of asteroids, comets, and other debris that envelops the solar system.
In the Sol system, it starts outside of Pluto's orbit and extends in a giant sphere surrounding the sun.
The edge of a star’s Oort cloud is essentially the edge of the star’s gravity well.
The Bobs consider a system’s Oort Cloud as the boundary between the system and interstellar space.