At the heart of our galaxy's center is SagA*,a supermassive black gap containing about four million solar-masses of material. SgrA* is relatively faint, unlike the supermassive black holes in some other galaxies. This is probably because, and unlike its active cousins,it is not aggressively accreting material and so is neither heating up its environment nor ejecting particularly intense jets of fast-moving charged particles. Of course, it is also faint because it is located about twenty-five thousand light years from soil and because it is shrouded in absorbing, and intervening dust. Nevertheless,radiation at radio, submillimeter, or infrared and X-rays can penetrate the veiling material. As the closest super massive black gap to soil,SgA* is a template for astronomers actively studying black holes, offering the best views of the physical properties and environments. The radio emission in specific is thought to approach from material falling onto a disk around the black gap and heating up electrons, and from ejected material both within the jet itself and its nozzle.
Source: phys.org