Here's why:
* Planets orbit stars. The Moon orbits the Earth.
* Planets are much larger than moons. Even the smallest planet in our solar system, Mercury, is significantly larger than the Moon.
However, there are a few moons in our solar system that are comparable in size to the Moon:
* Ganymede (Jupiter's moon) is the largest moon in our solar system and is even bigger than the planet Mercury.
* Titan (Saturn's moon) is the second-largest moon and is larger than the planet Mercury.
* Callisto (Jupiter's moon) is slightly smaller than Mercury.
So while there are no planets the size of the Moon, there are moons that are similar in size.
