Comet

Comets consist of a solid nucleus made of rock, dust, ice, and frozen gases like carbon dioxide, carbon monoxide, and ammonia. They are thought to originate from the cold, dark outer regions of the solar system. Comets become visible when their elliptical orbits bring them close to the Sun, causing the frozen gases to vaporize.

What happens to comets when they approach the Sun?

What is the significance of a comet's elliptical orbit?