In a model of the solar system, the reference point is the center of the model, which usually represents the Sun.

Here's why:

* The Sun is the center of our solar system: All planets, dwarf planets, asteroids, and other celestial bodies orbit the Sun due to its massive gravitational pull.

* Models should reflect reality: A model of the solar system aims to represent the actual arrangement and movement of objects in our solar system. Placing the Sun at the center accurately reflects this reality.

While you could technically choose a different reference point in a model (like a specific planet), doing so would make the model less accurate and harder to understand.