Timothy Ferriss, Seeing in the Dark
Quasars (the black holes at the centre of galaxies) are so luminous that if one was in action in a local group galaxy its brilliance would rival that of the Sun.
The Universe Story by Brian Swimme and Thomas Berry
In the centre of our own Milky Way galaxy a black hole churns, sucking suns into its destruction as a spider at the centre of a net transforms brilliant insects into black tombs.
The Universe Story by Brian Swimme and Thomas Berry
When we examine the nature of the universe we find galaxies with a violence so intense that we cannot account for it scientifically: great spikes of energy blasting across hundreds of millions of miles from centre of the galaxy out through its member systems. Speculation points to black holes of monstrous dimensions generating such extremes of energy from the centre of the galaxy. Our own Milky Way Galaxy might be capable of generating such a death spike. If such an energy blast does erupt, we will not learn all that much before it reaches us. Even now, a wall of plasma could be rifling towards us at millions of miles a minute; with some stupendous power it would not even notice the Sun and Earth as it scattered us into elementary particles in its inexorable flight of destruction through the stellar systems.
http://jila.colorado.edu/~ajsh/insidebh/intro.html
https://www.reddit.com/r/askscience/comments/awzjhv/what_is_the_whiteness_around_the_black_hole/
The latest simulations suggest that they look like this
How dense are they?
If you compressed our Sun into a sphere of roughly 3km radius it would become a black hole, but the Earth's orbit would remain completely unchanged because the mass at the center of our solar system remains unchanged.
From <https://www.reddit.com/r/AskScienceDiscussion/comments/azzfnq/are_there_unknown_features_of_black_holes_that/>