- #1
iMatt
- 10
- 1
Simple "Beginner" Dark Matter Question
Ok, for some reason I can't seem to get this straight, probably because its so obvious nobody spells it out. Its more a question of terminology than the real mystery of dark matter, but its proving an obstacle in my efforts to catch up on a subject i have recently become interested in.
Very simple explanations of the existence of dark matter will often say that there isn't enough visible matter in galaxies such as ours to explain what holds it together. This leads, eventually, to the idea of a dark matter Halo etc. Now, the simple question is this: when such people talk about the visible matter in the galaxy, does this include the supermassive black hole at its centre? In other words, is this black hole considered to be part of the "observable" galaxy, or is this considered to form a part (but clearly not all) of the dark matter that holds the galaxy together.
As simple as it sounds I have tried and failed to get this clear in my mind. I have come across discussions of whether the unknown dark matter outside the galaxy might comprise or include small black holes - but this is a different issue. My question is more straightforward - are the black holes we are aware of, in our own galaxy for instance, counted as part of the "observable" component of matter, or do they get lumped in with the dark matter component?
Hoping you can straighten me out.
Thanks
Ok, for some reason I can't seem to get this straight, probably because its so obvious nobody spells it out. Its more a question of terminology than the real mystery of dark matter, but its proving an obstacle in my efforts to catch up on a subject i have recently become interested in.
Very simple explanations of the existence of dark matter will often say that there isn't enough visible matter in galaxies such as ours to explain what holds it together. This leads, eventually, to the idea of a dark matter Halo etc. Now, the simple question is this: when such people talk about the visible matter in the galaxy, does this include the supermassive black hole at its centre? In other words, is this black hole considered to be part of the "observable" galaxy, or is this considered to form a part (but clearly not all) of the dark matter that holds the galaxy together.
As simple as it sounds I have tried and failed to get this clear in my mind. I have come across discussions of whether the unknown dark matter outside the galaxy might comprise or include small black holes - but this is a different issue. My question is more straightforward - are the black holes we are aware of, in our own galaxy for instance, counted as part of the "observable" component of matter, or do they get lumped in with the dark matter component?
Hoping you can straighten me out.
Thanks