920-Cometary Rocket

Viewed in a telescope an asteroid appears as a moving star like point of light while  a comet often appears to be a fuzzy point of light with a tail.  The orbit of an asteroid is governed force of gravity exerted by the Sun, planets, and in some cases our moon. In addition the Yarkovsky Effect can cause the orbit of a spinning asteroid to shift slightly over millions of years as the heat it absorbs from the Sun radiates back into space. Comets on the other hand can have orbits which change erratically as its nucleus emits small rocket like bursts when frozen gases trapped within it are heated by the Sun.