Caption: Sagittarius A* (Sag A*) and its environment as imaged in the X-ray (and therefore false-color) by Chandra X-ray Observatory (1999--).

Features:

1. Sag A* is an intense compact radio source surrounding, more or less, the Milky Way center black hole, a supermassive black hole of mass ∼ 4.3 M_☉.

   Sag A* is also an X-ray source evidently.

2. The electromagnetic radiation (EMR) from Sag A* is provided by the interstellar medium (ISM) swirling into center black hole: gravitational potential energy gets converted to kinetic energy which viscosity and shocks convert to heat energy which is radiated as thermal radiation.

   There may be some non-thermal EMR too---but yours truly must look this up.

3. The center black hole is very nearly at the center of mass and bottom of the gravitational well of the Milky Way. I'm not sure if we know how close it is to these things.

4. Can we ever revolve an event horizon and see a black hole as a black hole?

   For stellar-mass black holes, this seems very unlikely. They are all much too far away and too small to resolve.

   But may be possible to resolve the supermassive black hole at the Galactic center.

   In fact, there is a plan to resolve this supermassive black hole (which can be called the Galactic center black hole and which is located the astronomical radio source Sagittarius A*) by perhaps 2016 (see Wikipedia: Event Horizon Telescope).

   See the figure below. The EHT is a project that uses a global array of radio telescope to try to image the neighborhood of the