The study of planets and stars falls under the domain of astronomy.

Here's a breakdown:

* Astronomers are scientists who study celestial objects like planets, stars, galaxies, and the universe as a whole.

* Astrophysicists specialize in the physical properties of these objects, focusing on their composition, evolution, and the laws of physics that govern them.

So, while both astronomers and astrophysicists study planets and stars, they often focus on different aspects of these celestial bodies.