Quasars: Millisecond-of-Arc Structure Revealed by Very-Long-Baseline Interferometry.

Observations with the Goldstone-Haystack radio interferometer of the quasars 3C 279 and 3C 273 have disclosed the presence of fine structure in their radio emissions. Although the interpretation is not unique, the fringe-amplitude data for quasar 3C 279 are quite consistent with emissions from two points, each contributing equally to the correlated flux. The separation of the two points is estimated to be (1.55 +/- 0.05) x 10(-3) arc second, or about 20 light years at the distance of 3 x 10(9) light years inferred from optical red-shift data. The formal uncertainty in the right-ascension component of the separation is about 6 x 10(-6) arc second; differential proper motion in this direction at half the speed of light could be discerned within a year. The fringe-amplitude data of quasar 3C 273 allow similar, but less definitive, interpretations.