Astrometric binaries are a type of binary star system where one star is visible, while the other is detected through its gravitational influence on the visible star. This influence causes the visible star to move in a wobbly path, which can be observed over time. By studying these movements, astronomers can infer the presence of the unseen companion and determine its mass and orbit. These systems are important for understanding stellar masses and dynamics. They often involve stars like Sirius, which is a well-known astrometric binary. The study of astrometric binaries contributes to our knowledge of stellar evolution and the formation of star systems.