astrometric binary

An astrometric binary is a pair of stars that orbit each other, but only one is visibly observed. The unseen companion influences the visible star’s motion, causing slight shifts in its position over time. By carefully measuring these tiny movements, astronomers can infer the presence of the hidden companion and estimate its mass. Essentially, it's like detecting a dance partner you can't see directly, based on how the visible star moves around a common center of mass, revealing the binary system through precise positional measurements.