What type of movement does the Astrometry method precisely measure to infer a planet's presence?

Answer

A star's side-to-side or up-and-down position shift relative to background stars

Astrometry measures the precise position of a star in the sky over time, detecting the subtle side-to-side displacement caused by the gravitational pull of an orbiting planet relative to fixed background stars.

What type of movement does the Astrometry method precisely measure to infer a planet's presence?
astronomyorbitstarexoplanetdetection