When our star Sun was young small countless planetesimals
orbiting coalesced conjoined and aggregated to form
bigger planetoids larger midget planets and very large
planets..
Smaller starfish like rocky planetoids are called asteroids
Most of the known asteroids are orbiting the Sun in-between the
orbits of Mars and Jupiter..
Sans satellites and rings of their own system by definition
planets had cleared such smaller orbiters at the least in
the space between (nearest-to-Sun) perihelion and ( farthest-from-
Sun ) aphelion.
Very large Ceres recent discovery Vesta and very massive Apophis
are notable among the innumerable asteroids.