A binary star in which the presence of an invisible or unresolved component is inferred from irregularities in the proper motion of the visible component. Similarly, a known binary star may prove to be an astrometric multiple star. Some astrometric binaries have subsequently been resolved by speckle interferometry. Components calculated to have extremely low mass may be either faint red dwarfs, brown dwarfs, or possibly even planets.
astrometric binary: The presence of an unseen companion causes a visible star to wobble from side to side as it moves through space.
Subjects: Astronomy and Astrophysics.