What do we call a large system that contains many stars?

A large system that contains many stars is called a galaxy. Galaxies are vast collections of stars, gas, dust, and dark matter, bound together by gravity. They vary in size and structure, with some containing billions of stars while others may have just a few million.

The term "universe" refers to everything that exists, including all matter, energy, planets, stars, galaxies, and even the space between them. It encompasses all galaxies and is much broader than the term galaxy itself.

A cluster is a smaller group of galaxies that are held together by gravity. Clusters can contain anywhere from a few to thousands of galaxies, making them a step smaller than a galaxy in terms of scale.

A constellation, on the other hand, is a pattern of stars in the night sky as observed from Earth. It does not refer to a physical system like a galaxy but is rather a human-made grouping of stars that often tells a story or represents specific figures in mythology.

Thus, the most accurate term for a large system containing numerous stars is indeed a galaxy.