Here's why:

* Stars are giant balls of hot gas (mainly hydrogen and helium) that undergo nuclear fusion in their cores. This process releases immense energy in the form of light and heat.

* Planets are celestial bodies that orbit stars. They don't have their own internal energy source and reflect the light they receive from their star.

Think of it this way:

* Stars are like giant, self-powered lamps that illuminate the universe.

* Planets are like mirrors that reflect the light from the stars.