位于银河系中央的极其致密的非热射电源SagittariusA^*(SgrA^*),被公认为是最佳的超大质量黑洞候选体,其质量约为400万个太阳质量。甚长基线干涉测量(VLBI)技术以其独有的高空间分辨率为我们提供了唯一可以探讨SgrA^*位于几个史瓦西(Schwarzschild)半径区域内天体物理性质的手段。介绍了对SgrA^*的VLBI研究现状和最新进展,着重论述了毫米波和亚毫米波VLBI观测对研究SgrA^*的辐射区域的真实形状和大小,以及探索其结构随时间变化的重要性。SgrA^*无疑是检验广义相对论效应的亚毫米波VLBI实验的最佳目标。

There is compelling evidence that the extremely compact non-thermal radio source at the center of our Milky Way Galaxy, Sagittarius A^* ( Sgr A^*), is a best known supermassive black hole candidate with a dark mass of 4 million solar masses. Very Long Baseline Interferometry (VLBI) technique, with its high-resolution imaging capability, is proved to be the most powerful tool for probing the region of a few Schwarzschild radii of Sgr A^*. This paper updates the progress in the VLBI observations of Sgr A^*, with the emphasis on the importance of the millimeter and sub-millimeter VLBI observations in the detection of the intrinsic structure of Sgr A^* and in our ongoing effort to search for the structural variability. There is no doubt that Sgr A^* would be the most important target for the future sub-millimeter VLBI experiment to test the General Relativity.