Comets are made of dust and ice that has accumulated at the fringes of the solar system. The gravity of the sun or other object sometimes perturb comets into a long orbit that brings it towards the sun. If the comet is made of ice that vaporizes when heated, why do you think comets form tails as they approach the sun? What direction do you think the tail goes, directly behind the comet from the direction it is moving, or directly away from the sun?