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View Full Version : Were "super massive" black holes ever stars?



snabald
2006-Feb-06, 04:42 AM
I was just wondering about the super massive black holes at the center of galaxies, where they ever super (hyper?) massive stars at some point in the distant past? If not are there any theories on where they came from?

ngc3314
2006-Feb-06, 06:01 PM
I was just wondering about the super massive black holes at the center of galaxies, where they ever super (hyper?) massive stars at some point in the distant past? If not are there any theories on where they came from?

Aye, there's the question! There is still a good bit of headscratching over what the seeds for these black holes cold have been. Once one reaches, say, tens of thousands of solar masses, it will grow in a galaxy environment through tidal disruption of stars and accretion of some of the gaseous debris. However, it's not so clear how something smaller gets to that point. You could imagine starting with the black-hole remnant of a Population III star, which might have as much as 100 solar masses - if surrounded by a dense enough gaseous environment, it could grow exponentially (with a pretty long time constant, but perhaps fast enough). Also, one could get a single massive black hole (in the thousands of solar masses, anyway) from collapse of a dense star cluster, one with plenty of neutron stars and stellar-mass black holes by the time the stars have run through some millions of years. If the cluster is dense enough (a so-called relativistic star cluster), there are a wide range of initial conditions which lead to runaway gravitational collapse. There's even a new theory paper out which proposes that dark matter could fall straight into a seed black hole within a certain radius (a degenerate configuration, for those keeping score) and thereby grow them very rapidly.

If you're bit confused, that may mean you understand the current state of the field accurately...

Ken G
2006-Feb-06, 06:07 PM
If you're bit confused, that may mean you understand the current state of the field accurately...
Perhaps this brings up another issue, which is, do the initial runaway black holes derive primarily from normal matter or dark matter (I presume by the end of the day the supermassive BHs are mostly from dark matter, but maybe even that isn't certain)? And then, how well does the "no hair" constraint on black holes manage to constrain the properties of dark matter (i.e., could dark matter have a different kind of "hair" than anything we've considered so far?)

Nereid
2006-Feb-07, 12:32 AM
A personal view (not backed by anything other than speculation): given that the nature and origin of dark matter is unknown (beyond that is 'cold', reacts but weakly - at best - with baryonic matter, and is a form of mass), its role in the formation SMBH that were - in one way or another - seeds for early quasars could be important. Further, the nature of any such role is essentially unconstrained by the observations we have, today.

A second bite of this cherry: the Standard Model (of particle physics) gives us enough to model matter/radiation soups ... up to a certain temperature (GeV? TeV?). Beyond that, the territory is increasingly unknown. But inflation ended when the temperature was what, ~10 OOM higher? Were the seeds of the SMBH at the hearts of (most) quasars and (some) galaxies sown in this realm?

Blob
2006-Feb-07, 12:58 AM
Hum,
Yes it is possible that super massive black holes at the centre of galaxies, were super (hyper?) massive stars at some point in the distant past

The problem is of course that the stellar blackholes created by such processes do not attract the surrounding matter (dust and hydrogen etc clouds) anymore than the star that created it. The process would take too long (ie. more than 750 million years)

It requires cold darkmatter (slow moving) - or perhaps imperfections in space-time - to seed, and speed up the gravitational collapse of such primordial and hot clouds.