View Full Version : How did Supermassive black holes get to the center of galaxies?

2015-Oct-28, 10:57 AM
I understand how black holes form...from stars that die with masses much larger than the sun. This explains stellar mass black holes more than SMBH.
My question is did the universe have enough time from stars that were probably a lot larger than we've ever seen now when the universe young and these black holes merged to form SMBHs and also why, if that's how SMBHs formed did they migrate to the center of galaxies?

The biggest stars were at the center of galaxies? What drew merging black holes to the center of galaxies to form SMBHs? Why are they at the centers and not randomly on the edge or outside of galaxies?

It sounds like that there's something different about SMBHs from stellar mass black holes more than they just form from massive stars that died?

A: Did they have enough time in the 13.5 billion year universe to get billions of times more massive than the sun.

B: Why do they always go to the center of a galaxy?

2015-Oct-28, 11:38 AM
I have the impression that however they form, they start in the centers of galaxies rather than migrate there.


The origin of supermassive black holes remains an open field of research. Astrophysicists agree that once a black hole is in place in the center of a galaxy, it can grow by accretion of matter and by merging with other black holes. There are, however, several hypotheses for the formation mechanisms and initial masses of the progenitors, or "seeds", of supermassive black holes. The most obvious hypothesis is that the seeds are black holes of tens or perhaps hundreds of solar masses that are left behind by the explosions of massive stars and grow by accretion of matter. Another model involves a large gas cloud in the period before the first stars formed collapsing into a “quasi-star” and then a black hole of initially only around ~20 M☉, and then rapidly accreting to become relatively quickly an intermediate-mass black hole, and possibly a SMBH if the accretion-rate is not quenched at higher masses.[7] The initial “quasi-star” would become unstable to radial perturbations because of electron-positron pair production in its core, and may collapse directly into a black hole without a supernova explosion, which would eject most of its mass and prevent it from leaving a black hole as a remnant.

Yet another model[10] involves a dense stellar cluster undergoing core-collapse as the negative heat capacity of the system drives the velocity dispersion in the core to relativistic speeds. Finally, primordial black holes may have been produced directly from external pressure in the first moments after the Big Bang.

2015-Oct-28, 02:00 PM
Going a little further with what Noclevername has said: The issue of how galaxies, and the SMBHs, and even the dark matter halos they are embedded in form is something of an open question that current and near future research is narrowing in on through observations and simulations. I think it will be found that the SMBHs formed close to, but not necessarily in the exact centers of the dark matter halos, and their formation and growth depended on the flow of normal matter along intergalactic filaments. The interactions of the SMBHs with the dark matter halos would tend to have a damped process that would center the SMBH over an extended period (small billions of years?). A similar mechanism would be necessary to support the merging of SMBHs as galaxies merge.

2015-Oct-31, 03:50 PM
B: Why do they always go to the center of a galaxy?

Go? Why don't you think the galaxy formed around the SMBH?