The one is an artist conception from NASA/JPL-Caltech showing a supermassive black hole at the center, surrounded by matter flowing onto the black hole in an accretion disk. This disk forms as the dust and gas in the galaxy falls onto the hole, attracted by its gravity:
It was used in a report on a recently discovered super massive black hole that is so super massive that it pokes a hole into the current theory on the growth of black holes, even.
Another artist conception focuses on a binary system where one star has collapsed into a black hole and eats its companion (a phenomena earlier referenced in this blog). It is from the wikipedia entry on the accretion disc:
An actual image of the phenomena captured with the Hubble Telescope by L. Ferrarese of Johns Hopkins University and NASA is also listed in the same entry:
Other NASA concept drawings are available on the wikipedia commons. This one focuses on the center of the accretion disc where the event horizon shows itself as the light sucking center of the formation leading to the singularity where all current theories are broken down into hints, whispers, conjectures and shrugs:
The last diagram, from a Inspirehep.net a high energy physics publication of a short article by Volker Beckmann (Francois Arago Centre / APC Paris) and Chris R. Shrader (NASA/GSFC), shows that Active Galactic Nuclei (AGN) will look differently as differing angles of site. Particularly interesting to me is the inclusion of one of the most compelling abstract shapes of all, the torus, here in cross-section representing the dusty absorber around the accretion disc:
