Here's why:

* Icy ball: Comets are primarily made of ice, dust, and frozen gases.

* Elliptical orbit: Comets have highly elliptical orbits, meaning they travel in a very stretched-out oval shape. This causes them to spend most of their time far from the sun, but then swing in close during a brief period, often becoming visible to us as they heat up and release gas and dust.

Let me know if you have any other questions!