Here's how:
* "The Northern Lights" (Season 1, Episode 9): This episode features the Northern Lights, which are caused by a comet. While not explicitly explained, the phenomenon is shown to be a celestial event of great beauty and significance in the Fire Nation's culture.
* "The Day of Black Sun" (Season 2, Episode 7): This episode revolves around the "Day of Black Sun," a solar eclipse caused by a comet passing between the Earth and the Sun. This event leads to the Fire Nation's vulnerability to the other nations' attacks.
While these episodes don't provide a detailed explanation of comets, they highlight their impact on the world of Avatar and its people. The show's creators likely avoided a dedicated explanation of comets to focus on the primary narrative and characters, but they utilized the concept to drive plot points and add depth to the world-building.