by Chris Peterson » Fri Sep 06, 2013 9:38 pm
mjimih wrote:Did our black hole grow early on with a higher ratio of/more heavier material around? And now in a more mature galaxy, it consumes more light objects?
It's not well understood how supermassive black holes form. There is the "galaxy came first" suggestion, and the "black hole came first" suggestion. In the second case, there may have been a higher density of material, but it was certainly lighter, since this would have been before many elements heavier than hydrogen or helium would have existed.
In a mature galaxy, a central black hole only consumes objects when conditions are right for the formation of an accretion disc. Otherwise, there's no mechanism to rob orbiting material of angular momentum, and anything under the gravitational influence of the black hole will orbit, not fall inwards. There is evidence that galactic black holes go through cycles of consumption, as accretion discs form and are destroyed. Also, it's unlikely that in most cases the central black holes will ever consume more than a tiny fraction of the material in the rest of the galaxy. For the most part, their growing days are over.
[quote="mjimih"]Did our black hole grow early on with a higher ratio of/more heavier material around? And now in a more mature galaxy, it consumes more light objects?[/quote]
It's not well understood how supermassive black holes form. There is the "galaxy came first" suggestion, and the "black hole came first" suggestion. In the second case, there may have been a higher density of material, but it was certainly lighter, since this would have been before many elements heavier than hydrogen or helium would have existed.
In a mature galaxy, a central black hole only consumes objects when conditions are right for the formation of an accretion disc. Otherwise, there's no mechanism to rob orbiting material of angular momentum, and anything under the gravitational influence of the black hole will orbit, not fall inwards. There is evidence that galactic black holes go through cycles of consumption, as accretion discs form and are destroyed. Also, it's unlikely that in most cases the central black holes will ever consume more than a tiny fraction of the material in the rest of the galaxy. For the most part, their growing days are over.