Key points are not available for this paper at this time.
The compact continuum radio source Sgr A(*) associated with the center of the Galaxy appears unresolved at 86 GHz on a Kitt Peak, Arizona to Owens Valley, California Very Long Baseline Interferometer (VLBI). The lack of structure on this 850 km (2 x 108 lambda) baseline sets an upper limit on the angular size of 0.2 mas. The lack of a detection on the much longer baselines to the Haystack Observatory 37 m sets a lower limit of 0.1 mas on the angular size. Both limits are consistent with the angular size of 0.16 +/- 0.01 mas expected from the wavelength-squared dependence of size observed at longer wavelengths produced by diffractive scattering in the intervening turbulent plasma close to the Galactic center. The upper size limit implies an intrinsic size for the emitting region of less than 0.13 mas (1 AU) and a brightness temperature in excess of 1.4 x 1010 K.
Rogers et al. (Sat,) studied this question.