... info about active galactic nuclei ...
Thanks for the additional enlightenment, Art. Your comments also led me to another web page: http://astronomy.swin.edu.au/cosmos/G/Galactic+Nuclei
, which is a short but helpful article about the subject. (Not really new, though, it coincides with what has been said in this thread by you and Chris.)
I guess what I'm talking about, which is more "meditation" than science, is something I find interesting.
And now that I think about it, in this aspect, the center of a galaxy has a lot in common with the center of a solar system.
- In both cases, you have a body at the system's center of mass that is gravitationally huge. Indeed, a very dangerous place, that humans would not enjoy. Something quite awful would happen to us even before we could actually get there.
- But when we look at this point, and indeed our eyes are drawn to this point, instead of seeing a place where there is just a darkness and a crushing into oblivion, in both cases these are places of intense luminosity. In both cases mind-boggling amounts of energy stream out.
- And, unlike a fire burning on earth, they last and last, able to radiate out this energy for billions of years. Maybe this last point is not so strange. It is thanks to gravity, in both cases, having been the quiet collector, working across vast regions, to prepare the fuel for the furnaces of the cosmos.
So, in a sense, a galactic nucleus is much like our Sun (in effect, not in mechanism), but in a far bigger way. And, apparently, across more of the electromagnetic spectrum than a single star.
One of the differences
, I guess, is that our galactic nucleus is growing in mass through this process (well, the central black hole must be growing, I'm not sure if the galactic nucleus is or not), whereas our Sun does not. I have seen the term "feeding", for active galactic nuclei. But another thing I am unsure of here is whether or not a galactic nucleus actually has to consume matter to give off bursts of radiation. Perhaps the overall process need only capture a small portion of the mass it is "feeding on" when it is active.