Here's why:

* Icy objects: Comets are primarily composed of ice (water ice, frozen gases like carbon dioxide, methane, and ammonia), mixed with dust and rock.

* Light up the night sky: As a comet gets closer to the Sun, the heat causes the ice to vaporize. This creates a glowing cloud of gas and dust around the comet's nucleus, called a coma, which reflects sunlight and becomes visible.

* Close to the sun: The closer a comet gets to the Sun, the more intense the heat, leading to a brighter and more spectacular display.

Let me know if you'd like to learn more about comets!