Estimating the apparent motions of extragalactic radio sources

The apparent motions of 573 extragalactic radio sources are estimated. For this purpose, we analyzed the data that were obtained during 3193 series of observations using very-long baseline radio interferometry (VLBI) from 1984 to 2010. To find a solution, the least-squares method with constraints is applied. It is shown that most radio sources (including defining sources) are characterized by significant apparent motions. Since the stability of the celestial reference system is due to the absence of net rotation (no-net-rotation condition) relative to the defining sources, a change in their coordinates leads to the rotation of the celestial coordinate system (CCS). Owing to this, we believe that the apparent motions of radio sources must be given in catalogs.