For 10 points, name this phenomenon that gives its name to part of the "parsec" unit.
Jacobus Kapteyn was the first to use "statistical" data from this concept, and not "secular" data to gauge the layout of stars in the sky. A catalogue of stars' proper motion and values for this quantity was made using data from the Hipparcos satellite. This phenomenon gives its name to a trigonometric method in which distance to a faraway object is inferred using measurements of objects taken at intervals of six months, and then calculating the (*)  angle subtended by that object. A unit of measurement named for this phenomenon is approximately equal to 3.26 light-years. This term refers to the phenomenon of an object appearing to move when viewing it from two different lines of sight. For 10 points, name this phenomenon that gives its name to part of the "parsec" unit.
Jacobus Kapteyn was the first to use "statistical" data from this concept, and not "secular" data to gauge the layout of stars in the sky.
 parallax  [accept stellar  parallax  or statistical  parallax  or solar  parallax ]