hanuman wrote:Correct me if I'm wrong, but our system's asteroid belt is the remnant of a planet that broke up sometime in the past, right? In that case, no, not all star systems would have asteroid belts of their own.
However, all systems will have vast quantities of asteroids distributed throughout the system, as ours does. That'd be because most 'free' asteroids (not part of the belt) are the remains of the primordial dust cloud from which the sun and the planets have formed, if I'm not mistaken. I might be, so don't take my word for it.
Everything in the solar system is a product of the primordial dust cloud. We believe the cloud contracted until it's gravity was intense enough to pull most of the rest of the cloud in, then exploded to become the sun. We then believe the sun then threw out many of the heavier elements formed during it's creation, forming the Acretion disk. The Acretion disk started to clump together under the constitutant parts' gravity, causing the planets to form.
The planets then fought for stability, gobbling up each other, disturbing each other's orbits and colliding with each other. (The current mainstream belief is Jupiter's gravity destabilized and then threw a mars-sized proto planet inward which collided with the proto Earth, creating the Earth and Moon as we know them today.)
Most of the inner solar system detrius is believed to be created at this point - not from the primordial cloud or the Acretion disk itself, but from the collisions after and during the planetary formation.
The Oort Cloud and Kuiper belts are a completely different beast - these are the OLD items thrown so far out that even when they clumped, they were too far apart to interact "much" with each other, let alone the major planets. These are believed to be from at least the Acretion disk.