Here's why:

* Loose collection of rock and frozen gas: Comets are made up of ice, dust, and rock. The ice is mostly water ice, but it can also include frozen gases like carbon dioxide, methane, and ammonia.

* Tail: As a comet gets closer to the Sun, the ice starts to vaporize, creating a glowing tail of gas and dust that stretches out behind it.

Let me know if you have any other space mysteries you want to solve!