barycenter
/ˈbɛriˌsɛntər/
noun
- The center of mass of two or more bodies that orbit each other, such as a planet and its moon.
- The barycenter of the Earth-Moon system lies inside Earth, but not at its center.
- When two stars orbit a common barycenter, they are called a binary system.
- Astronomers calculate the barycenter to understand how planets move around a star.