The physical science that deals with stars and planets is astronomy.

Here's why:

* Astronomy is the study of celestial objects and phenomena. This includes:

* The origin, evolution, and properties of stars, planets, galaxies, and other celestial bodies.

* The laws of physics that govern the universe.

* The composition and structure of the universe.

While other sciences like physics and geology contribute to understanding the universe, astronomy is the primary field that specifically focuses on stars and planets.