You're right to think about that! Planets don't produce their own light like stars do. We see them because they reflect sunlight.

Here's how it works:

* Sunlight: The sun is a giant ball of hot gas that emits a tremendous amount of light and heat.

* Planets: Planets are celestial bodies that orbit stars. They don't generate their own light.

* Reflection: When sunlight hits a planet, some of it bounces back towards us. This reflected light is what we see when we look at a planet through a telescope or even with our naked eye.

Think of it like this: Imagine shining a flashlight on a ball. The ball itself doesn't emit light, but we can see it because the flashlight light reflects off its surface. The same principle applies to planets!

The brightness of a planet depends on factors like:

* Distance from the sun: Planets closer to the sun receive more sunlight and therefore appear brighter.

* Size: Larger planets reflect more sunlight and appear brighter.

* Composition: The surface of a planet (rocky, icy, gaseous) affects how much light it reflects.

So, we see planets because they act like giant mirrors, reflecting the sun's light back to us.