Here's a breakdown:

* Astronomers study celestial objects like stars, planets, galaxies, and nebulae. They use telescopes and other instruments to observe these objects and gather data about their properties, composition, evolution, and interactions.

While astronomers are the primary focus, other scientists contribute to our understanding of stars and planets:

* Astrophysicists specialize in the physics of celestial objects. They use their knowledge of physics to explain the processes occurring in stars, planets, and other celestial bodies.

* Planetary scientists focus specifically on the study of planets within and outside our solar system. They investigate their formation, composition, atmospheres, and potential for hosting life.

* Cosmologists study the universe as a whole, investigating its origin, evolution, and large-scale structure.

So, while all these scientists contribute to our understanding of stars and planets, the term astronomer encompasses the broadest range of study within this field.