A heavenly body composed of a nucleus of ice and dust and, when near the Sun, a tail of gas and dust particles pointing away from the sun is a/an comet.A small, rocky body orbiting the Sun is called a/an asteroid.rade 8 Small Bodies and Dwarf Planets. A heavenly body composed of a nucleus of ice and dust and, when near the Sun, a tail of gas and dust particles pointing away from the sun is a/an comet. A small, rocky body orbiting the Sun is called a/an asteroid.