Aberration

(Astron.). A slight alteration in the apparent position of a star, caused by the motion of the Earth in its orbit and the effect of that motion on the time required for the light of the star to reach the Earth.  The motion of the Earth across a ray of light causes a slight apparent change of direction, which altered angle is called the aberration of light-and to this is due the aberration of the star.  The effect is that each star appears annually to describe a minuet circle, of about 40.5”diameter, which runs parallel to the Earth’s diameter.