SIMBAD references

The fundamental celestial reference frame is realized by observations of extragalactic radio sources using the technique of very long baseline interferometry (VLBI). Compact radio-emitting active galactic nuclei are regularly used as reference points for relative positioning of other radio sources. VLBI absolute astrometric data indicate that the nucleus of the nearby radio galaxy J1147+3501 apparently changed its position by about 0.″02 some time between 1999 and 2017. We suggest that this unusually large displacement is a consequence of a drastic change in the source brightness distribution as revealed by archival high-resolution VLBI images.