Abstract

The 2021 Event Horizon Telescope observations resolve the innermost jet region of the blazar 3C 279 with unprecedented detail. The reconstructed images consistently reveal a compact core elongated nearly orthogonal to the large-scale jet axis. This rarely observed morphology recurs across multiple epochs and from 22-230,GHz and is therefore intrinsic rather than an imaging artifact. Geometric model fitting identifies several components with apparent speeds up to ̊m app ∼ 10, requiring bulk Lorentz factors Γ ≳ 10.3 and constraining viewing angles to extremely small values (łesssim 1^̧irc). Rest-frame brightness temperatures are systematically low (T_B ∼ 10^9--10^ 10 , ), consistent with optically thin emission at 230,GHz. These results suggest that the jet bends toward the observer on sub-parsec scales, producing strong relativistic beaming. Possible drivers of the observed jet bending and temporal evolution include the jet's interaction with the interstellar medium, kink or Kelvin--Helmholtz instabilities, magnetic reconnection near the horizon, or binary-induced precession. However, the current temporal coverage of VLBI data remains insufficient to distinguish between these mechanisms. Continued multifrequency VLBI monitoring will be essential to constraining the dynamics and geometry of the jet base in 3C 279. K