Here's why:
* Composition: Comets are essentially dirty snowballs made of ice (water, carbon dioxide, methane, etc.) mixed with dust and rock.
* Solar Heating: As a comet approaches the Sun, the solar radiation heats it up.
* Sublimation: The ice within the comet undergoes a process called sublimation, where it transitions directly from a solid to a gas without passing through a liquid phase.
* Cometary Tail: This vaporized ice and dust form the comet's characteristic tail, which points away from the Sun due to the pressure of solar wind.
With each trip around the Sun, the comet loses a bit of its icy material, causing it to shrink and eventually become less active.
