Intrinsic Size and Shape of Sgr A*: 3.6 AU by <1 AU
  By means of near-simultaneous multi-wavelength VLBA measurements, we determine for the first time the intrinsic size of Sgr A* to be 3.6 AU by <1 AU with the major axis oriented essentially north-south. Contrary to previous expectation that the intrinsic structure of Sgr A* is observable only at wavelength shorter than 1 mm, we can discern the intrinsic source size at 7~mm because (1) the scattering size along the minor axis is half that along the major axis, and (2) the near simultaneous multi-wavelength mapping of Sgr A* makes it possible to extrapolate precisely the minor axis scattering angle at 7~mm. The intrinsic size and shape place direct constraints on the various theoretical models for Sgr A*. 
K. Y. Lo (1), Z.-Q. Shen (1,2), J.-H. Zhao (3) and Paul~T. P. Ho (3)   ((1) Academia Sinica Institute of Astronomy & Astroph...