Observing the Time Evolution of the Multicomponent Nucleus of 3C 84

The advent of global millimeter-band very long baseline interferometry (VLBI) in recent years has finally revealed the morphology of the base of the two most prominent nearby, bright, extragalactic radio jets in M87 and 3C 84. The images are quite surprising considering the predictions of jet theory and current numerical modeling. The jet bases are extremely wide compared to expectations, and the nucleus of 3C 84 is very complicated. It appears as a double nucleus in 86 GHz observations with 50 μas resolution and a triple nucleus with 30 μas resolution with space-based VLBI by RadioAstron at 22 GHz. What is even odder is that the double and triple nuclei are arranged along an east-west line that is approximately orthogonal to the north-south large-scale jet on 150 μas-4 mas scales. We explore the emergence of an (east-west) double nucleus in the lower-resolution 43 GHz Very Long Baseline Array (VLBA) imaging from 2018 August to 2020 April. The double nucleus is marginally resolved. We exploit the east-west resolution associated with the longest baselines, ∼0.08 mas, to track a predominantly east-west separation speed of ≈0.086 ± 0.008c. We estimate that the observed mildly relativistic speed persists over a deprojected distance of ∼1900-9800 times the central, supermassive black hole gravitational radius (∼0.3-1.5 lt-yr) from the point of origin.