Here's why:

* Large solid masses: Planets are large celestial bodies made up of solid rock, gas, or a combination of both.

* Approximately spherical: Planets are massive enough that their own gravity pulls them into a nearly spherical shape.

* Revolve around the sun: Planets orbit the sun in a predictable path due to the sun's gravitational pull.

* Earth is the most famous: Earth is our home planet and the most well-known of the eight planets in our solar system.

Let me know if you have any more questions!