A binary star system in which one companion is invisible, but is known to be present from its effect on measurements relating to the other.
- ‘About a hundred astrometric binary candidates have been discovered by Hipparcos.’
- ‘As technology has improved over time, a number of binaries originally identified as astrometric binaries have been upgraded to visual binary because of the sighting of the secondary in the system.’
- ‘In astrometric binaries we see one star's position wobble periodically in response to the gravity of its unseen companion.’
- ‘During the period 1950 to 1970, a number of stars, most notably Barnard's star, were claimed to be astrometric binaries with substellar companions.’
- ‘Thus Sirius was originally an astrometric binary, but is now a visual binary.’