Measuring the shape of the Milky Way's black hole
At the heart of our galaxy's center is SagA*, a supermassive black hole 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, 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 Earth and because it is shrouded in absorbing, intervening dust. Nevertheless, radiation at radio, submillimeter, infrared and X-rays can penetrate the veiling material. As the closest super massive black hole to Earth, SgA* is a template for astronomers actively studying black holes, offering the best views of the physical properties and environments. The radio emission in particular is thought to come from material falling onto a disk around the black...