The exponential law for superluminal expansion of quasar 3C273

The radioastronomical technique of VLBI achieves an angular resolution better than 1 marcs, equivalent to a physical resolution of the order of light-years. In even the most distant galaxies such objects can be easily detected. In four extreme cases, three quasars (3C273, 3C279 and 3C345) and one seyfert galaxy (3C120) have been seen to expand with an apparent speed more than twice the speed of light. The evidence for such 'superluminal' expansion has been based on rather limited data, and the interpretation has been uncertain; but the recent development of the VLBI technique of hybrid mapping allows us to map the radio brightness distribution to show the expansion directly and unambiguously. This article uses the data of the quasar 3C273 presented earlier and presents a formula for the observation of superluminal expansion velocity of quasar 3C273. (Auth.)