<P> In the current Solar System, these small bodies are usually also classified by dynamics and composition, and may have subsequently evolved to become comets, Kuiper belt objects or trojan asteroids, for example . In other words, some planetesimals became other types of body once planetary formation had finished, and may be referred to by either or both names . </P> <P> The above definition is not endorsed by the International Astronomical Union, and other working groups may choose to adopt the same or a different definition . There is also no exact dividing line between a planetesimal and protoplanet . </P>

Theoretical spherical region of icy planetismals beyond the kuiper belt