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Fraser
2005-Feb-16, 05:48 PM
SUMMARY: Researchers have used the Chandra X-Ray Observatory to understand just how large supermassive black holes can get by performing a very detailed census of the mysterious objects. These are the gigantic black holes, with millions of times the mass of our Sun, that sit at the centre of almost every galaxy. The largest of them reach 100 million solar masses and gained this weight early - then they ran out of material to consume. The smaller holes, between 10 and 100 million solar masses, have been more frugal with the gas and dust they consume, and continue to grow to this day.

View full article (http://www.universetoday.com/am/publish/limit_black_holes.html)

What do you think about this story? Post your comments below.

Guest
2005-Feb-16, 05:59 PM
very nice info :)

Duane
2005-Feb-16, 07:45 PM
What an interesting observation! I am a little confused by the reasons behind the apparent mass limit. It seems odd to me that a black hole could have any limit on it's size. I mean, since the gravitational influence of the black hole would still affect nearby matter, drawing it to itself, what would stop that matter from falling into the event horizon?

Furthermore, if there is a galactic merger of two galaxies containing the very largest massed black holes, what could prevent them from merging? Or even if a smaller-massed black hole got caught up in the gravity well of one of these monsters, again, what could possibly prevent the two from merging togeather?

Maybe I'm reading this wrong?

antoniseb
2005-Feb-16, 07:54 PM
Originally posted by Duane@Feb 16 2005, 07:45 PM
It seems odd to me that a black hole could have any limit on it's size. I mean, since the gravitational influence of the black hole would still affect nearby matter, drawing it to itself, what would stop that matter from falling into the event horizon?
My take from the article was not that there is a theoretical limit, but a practical one. The mechanism that allows these things to form provides a certain range of mass of gas that could fall in. In galaxies with larger masses, this gas mostly falls in quickly, and in smaller ones, it appears to accrete more slowly.

The limiting factor may be the density of the Universe in the era that the SMBH's first started forming.

Guest_Fred
2005-Feb-16, 09:37 PM
So,
I am just wondering
What happens when they eat too much?
do they do the 'big bang' thing??
and start some new life somewhere???

antoniseb
2005-Feb-16, 10:46 PM
Originally posted by Guest_Fred@Feb 16 2005, 09:37 PM
So,
I am just wondering
What happens when they eat too much?
do they do the 'big bang' thing??
and start some new life somewhere???
There is no reason to think that a black hole could "eat too much". They consume what they can, and only stop "eating" when there's nothing left in the fridge.

StarLab
2005-Feb-17, 01:15 AM
...which is why the stomach is a bottomless pit.

greenone
2005-Feb-17, 06:41 AM
is it possible that above 100 million solar masses, all of the infalling matter is converted to energy before it can approach the event horizon? this might happen due to massive acceleration.

antoniseb
2005-Feb-17, 03:16 PM
Originally posted by greenone@Feb 17 2005, 06:41 AM
is it possible that above 100 million solar masses, all of the infalling matter is converted to energy before it can approach the event horizon? this might happen due to massive acceleration.
No. There are SMBHs over a 1000 million [billion unless you're English] solar masses. The point is that of the material that initially forms the galactic central bulge, eventually 0.001 of it becomes the central black hole. When this is done, there is nothing left for the SMBH to accrete, unless there are subsequent galaxy mergers, which is how the giants like M87 get formed.

When the initial proto-galaxies are forming, there typical size, and that governs the eventual size of the SMBH. Cosmic expansion prevents mergers from happening too frequntly, and limits it to only a few galaxies in the same cluster.

greenone
2005-Feb-17, 05:58 PM
antoniseb-

you have me at a loss, i can understand why the initial mass of a galaxy would govern the mass of the central black hole, but what is to stop additional matter from falling towards to galactic center thereby increasing the bh's mass?

unless i am missunderstanding this, there can be no "solar wind" from a black hole because of the gravitational pull. (never mind the x-ray jets they only eject material away from the plane of the ecliptic.

antoniseb
2005-Feb-17, 06:48 PM
Originally posted by greenone@Feb 17 2005, 05:58 PM
what is to stop additional matter from falling towards to galactic center thereby increasing the bh's mass?
Angular momentum is what stops it. If the matter were just sitting there, instead of orbiting the galaxy hosting the SMBH, of course it would fall in [which is how it forms in the first place]. But the SMBH can't suck in an orbiting star any more than the Sun can suck in the Earth, or the Earth suck in the Moon.

greenone
2005-Feb-18, 06:39 AM
i get it... thanks

GOURDHEAD
2005-Feb-18, 02:36 PM
Star density near the SMBH, even in a mature galaxy, should be such that they "gravitationally tug and bump" each other into trajectories that cause them to be captured by the SMBH unless there is an intervening force. Could that force be supplied by electric and magnetic fields of unusual strength such that, after reaching a threshold mass with commensurate spin, the environment prevents further capture of additional plasma? I really believe there is no upper limit to the mass of a BH irrespective of charge and spin. For specific charge and spin values there may be upper limits to masses.

antoniseb
2005-Feb-18, 03:20 PM
Originally posted by GOURDHEAD@Feb 18 2005, 02:36 PM
Star density near the SMBH, even in a mature galaxy, should be such that they "gravitationally tug and bump" each other into trajectories that cause them to be captured by the SMBH
It's likely that they are, and this may be the cause of the very short GRBs with no long afterglow. The frequency of capture is not apt to be very high, even with the expected densities. Keep in mind that the SMBH is comparable in size to our solar system. That's a pretty small target for rogue stars to hit.

some dude
2005-Feb-22, 03:52 AM
I reckon the blackholes will eventually suck the universe up, merge due to the gravitational attraction, create a monster motha hole, colide into an antimatter blackhole and make another bigbang :)

wstevenbrown
2005-Feb-22, 05:48 AM
The tugging and bumping, it should be emphasized, is not entirely gravitational-- near the event horizon, it's very crowded. When masses collide, some are speeded up, and some are slowed down. Think of it in two dimension, tho. The items which slow down lose tangential velocity, and begin to fall inward, gaining radial velocity, toward the center-- where it's more crowded, and the likelihood of further collisions is increased. Each time, the semi-minor axis of the orbit decreases, until finally, direct infall across the event horizon is inevitable.

All those collisions dissipate energy as heat, and as orbit radius decreases, temperature (and ionization) increases. Fast-moving ions generate magnetic fields, and the ions migrate toward the poles to form jets of outgoing material. There is Nobel jewelry available for anyone who can describe the process in step-by-step mathematical detail.

Just to keep it interesting, near the event horizon the velocities become relativistic-- at the event horizon, a velocity of c achieves a circular orbit. Inside the event horizon... well, there's a lot of discussion about that. It's those relativistic velocities that may limit how fast a black hole can eat (as perceived from outside), even more so than the amount of material available, or its clumpiness.

Most modern theorists seem to think that the Big Bang produced first energy, then particles, then condensed matter, in an isotropic distribution. Therefore, logically, all of the black holes (being accumulations of condensed matter) must have formed later. This is a model-dependent assumption, but using it as a basis, one could arrive at a largest possible BH by figuring out how fast they could form, how fast they could eat, and how long they've been eating.

Okay. But. What if some of the BH's were primordial, spewed out in an unknown mass distribution from the original bang? Then there would effectively not be a biggest possible BH, since we don't know what the largest starting value was. Fog looks isotropic too, when we're walking thru it. Best regards-- Steve :o

kevinbest83
2005-Feb-22, 01:30 PM
:( I am from Taiwan I like it very much :blink:

GOURDHEAD
2005-Feb-22, 01:47 PM
colide into an antimatter blackhole and make another bigbang This is an interesting concept that may be prevented if information is totally lost. The black hole will not "remember" the history of its constituents. The sub-quark soup comprising it may be without charge as we are accustomed to dealing with it.

With this in mind and if quantum tunneling across the event horizon is allowed, how will the escaping particles assume either a matter or anti-matter configuration? Could this be the source of "charge independent" i.e., dark, matter?