comet -celestial object consisting of a nucleus of ice and dust and, when near the sun, a tail of gas and dust particles pointing away from the sun.
asteroid-a small rocky body orbiting the sun. Large numbers of these, ranging enormously in size, are found between the orbits of Mars and Jupiter, though some have more eccentric orbits.meteoroid -small body moving in the solar system that would become a meteor if it entered the earth's atmosphere.
