How do black holes form in the middle of gallaxies?

Answer 1

That is a very good question, as this relationship is not well known. It is kind of like the conundrum of "which came first, the chicken or the egg." One might view the gravitational influence of the whole Milky Way galaxy as either just a product of its centric 'Black Hole' or as the complete synergistic grouping of all mass within the Milky Way galaxy that induced its centric black hole. Indeed, are errant black holes roaming the universe in search of a nebula to dominate ? or Are black holes induced upon the formation and focus of positive mass density?

Note: There exists variant theories for the existence of Black Holes; one hypothesis has Black Holes being created from the collapsed stellar core of larger than three solar masses, while another has black holes predating stars and forming upon the instance of the Big Bang. In fact, the concept of a star growing or shrinking has little to do with gravitational accretion. So if a Black Hole is just a converted state of stellar evolution, then should we expect that the Black Hole size should be dependent on the amount of material being attracted and annihilated upon its Event Horizon? Per the current consensus, there is not a relevant relationship between the observable size of the accumulated bulge about the Black Hole and the size of the Black Hole itself.

And considering the Black Hole radiation jets act as the safety valve for the reactions within a Black Hole, one might speculate that, like a star, the size of the Black Hole has more to do with its internal reactions and less to do with the matter being converted upon its Event Horizon. Still another such theory has their formations predating galaxies and or even predating normal matter itself, existing unto the moment of the Big Bang itself (i.e. unfolding of SpaceTime into a traditional fourth dimensional condition).

Answer 2

Black holes form in the middle of galaxies when a massive star collapses under its own gravity at the end of its life cycle. This collapse creates a singularity with an extremely strong gravitational pull that devours nearby matter and continues to grow in mass. Over time, these growing black holes can become supermassive and end up at the center of galaxies.