What constitutes a planetary system?

A planetary system is defined as a structure that includes a star, which is typically a central massive body, and various celestial objects that are bound by gravity to that star. These objects can include planets, which orbit the star, as well as smaller bodies like asteroids and comets. This definition is grounded in our understanding of how such systems form and evolve in the universe.

In contrast, the other options refer to different astronomical concepts. A group of stars forming a constellation does not imply any gravitational relationship akin to that in a planetary system. Similarly, referring to all celestial bodies within a galaxy describes a much broader category, encompassing various stars and systems, but not necessarily linking them by orbiting dynamics. Lastly, the concept of a collection of moons orbiting a planet pertains specifically to natural satellites of a planet rather than a complete stellar system that also includes a star and other orbiting bodies.