As arbitrarily as the distinction between meteoroids (see previous article) is the distinction between comets and asteroids. While meteoroids aren’t numbered or named at all because they are expected to burn in atmospheres anyway, comets are named, but don’t get an asteroid number. A comet is defined as showing emissions of light, observable as a tail, when close to the Sun. But when celestial objects are only composed of similar materials as other comets and not showing a tail, then they are still categorized as comets and called inactive in order to distinguish them from active comets. Sometimes celestial objects, that are believed to be asteroids, show emissions. In this case they are called active asteroids in contrary to inactive asteroids, but not re-categorized as comets. Hence the distinction is arbitrary. There isn’t any clear definition. In order to become an active object has an asteroid or a comet to bring some water with it. Only those asteroids, that are currently believed to be structured as rubble piles, shouldn’t have water and hence can’t become active and hence can’t be comets. But this is probably true for many satellites and about half of the independent asteroids.

By the way, space junk or space debris gets designations because it must be watched because different from asteroids or comets will a huge part (that in the lower orbits) of space debris definitely crash down on the surface of the Earth. Space debris is identified by an alphanumerical code.