What type of star system is characterized by two stars orbiting each other?

A binary star system is specifically defined as a system in which two stars orbit around a common center of mass. This characteristic of mutual gravitational attraction leads to various orbital patterns, which can be studied to understand stellar masses and distances. In a binary system, the stars are close enough that their interactions can significantly influence their motions and characteristics.

The significance of binary stars in astronomy lies in their ability to provide a more accurate measure of stellar mass. When astronomers observe the orbital period and distance between the two stars, they can apply Kepler's laws of motion to derive the mass of each star. This is particularly valuable as mass is a fundamental property influencing a star's lifecycle, evolution, and luminosity.

In contrast, a solar system consists of a star and all the celestial objects that orbit it, such as planets and asteroids. A galaxy is a massive system consisting of billions of stars, their solar systems, stellar remnants, and interstellar matter. An open cluster is a group of stars that are relatively young and loosely bound by gravity, often formed from the same molecular cloud. Each of these terms highlights different structures and relationships in the universe, while only the binary star definition specifically addresses two stars in orbit around each other.