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Black Holes May Not Grow Beyond Certain Limit
xyz writes "Do black holes increase in size indefinitely? According to an analysis by astronomers at Yale and the European Southern Observatory, the maximum size a black hole may reach is only few tens of billion of solar masses. The limit was calculated using an analysis of what may happen to the gas surrounding a black hole which has reached few tens of billions of solar masses. It is thought that black holes of such size heat the surrounding gas to a temperature where the radiation pressure begins blowing outer layers into space."
I am not an astrophysicist (IANAAP?), but this would seem to have some interesting implications for galactic mechanics. For one, does this means that stars are continously recycled by the black hole believed to be at the center of each galaxy? i.e. They get sucked in, crushed, then ejected as gassous emmisions which then collect and reform as a new star.
Wouldn't this also create a "galactic wind" similar to the solar wind experienced inside a solar system? Could such a wind (as weak as it may be on a micro scale) be responsible for the universe's apparent anti-gravity effect? It seems to me that if a galactic wind did exist, it would cause the galaxies to repel each other as the particles communicate back the forces of the particle collisions over billions of years.
Speaking of Black Holes, I was just listening to an interview with Brian Greene on NPR this morning. It seems that he has released a children's book designed to help children understand Relativity. Specifically, the link between gravity and time. Amazon has a nice video* where Mr. Greene explains the story and how he attempts to create an emotional connection between readers and the physics of Relativity.
* Full Disclosure: I did NOT include a referral code. This is a clean link
** Someone should really make a joke out of LHC doomsday and how we're all saved. I couldn't come up with anything funny.
Javascript + Nintendo DSi = DSiCade
It is thought that black holes of such size heat the surrounding gas to a temperature where the radiation pressure begins blowing outer layers into space.
Well, I'll admit this sounds intuitive with the Penrose-Hawking singularity theorems applied to the Big Bang. Now, I'm not a physicist either but I have read a lot that speculates the Big Bang was a singularity that created a hot unstable mess. All the mass of the universe in a singularity suddenly starts blowing out and producing massive heat. Although what was around this singularity is nothing--not even space.
As always, it brings up interesting questions about what was before that epoch since it is kind of clear that such a singularity could not be possibly be stable for any amount of time (as this research indicates).
** Someone should really make a joke out of LHC doomsday and how we're all saved. I couldn't come up with anything funny.
I was trying to relay what I had read about the micro black holes the LHC is trying to create to a female coworker. I failed. She told me someone in India committed suicide facing the LHC being turned on. All I could think of was that I really wish they called micro black holes that exist for minute fractions of a second something other than "black holes." It scares people unnaturally.
My work here is dung.
Stop spreading FUD, it's only a single ten of trillion.
You are forgetting the unfunded liabilities the American taxpayer is on the hook for which is $60+ trillion.
If you have something that you dont want anyone to know, maybe you shouldnt be doing it in the first place -Eric Schmidt
I'm sure I'm basing this on some bad sci fi movie or other, but can't two of these maxed out black holes merge together (in theory at least) to form a larger one?
What we today call MRI (Magnetic Resonance Imaging) used to be called NMRI (Nuclear Magnetic Resonance Imaging). As with "Black Holes", people were afraid of anything "nuclear"; hence the name change.
They're not saying that matter is ejected from inside the hole, so no, stars wouldn't be recycled. Also, they are not saying black holes at galactic cores are at this limit. Sagittarius A*, for example, which lies at the center of the Milky Way, is estimated to be only 3.7 million solar masses...orders of magnitude below this theoretical maximum. Also, such a wind as you suggest should be observable as it interacts with free gas and dust in the Milky Way. This may sound hard to believe, but it is in fact regularly observed in supernova remnants and massive stars like in the Crescent Nebula.
So what they're actually decribing is gas, dust, etc in the accretion disc orbiting near but not yet swallowed by the black hole. As stated, this gas becomes superheated and expands as it swirls ever closer to the hole. They claim that at some point the heat grows so intense that like a Wolf-Rayet star at the Eddington limit, it just blows all of the remaining gas away from itself to form a big bubble of relative emptiness. The article fairly descriptively labels this as a "dry" black hole. Actually, going back to the star recycling concept, this effect may be so dramatic as to actually prevent star formation in the host galaxy for the predictable future.
At this point I think the description is a little sloppy, since the black hole would then be devoid of material to compress and heat, and therefore the "black hole wind" (AC's insert crude fart joke here) effect is now gone. Theoretically then, feeding is able to occur at slow rates, and reading between the lines of the article, it sounds like the researchers agree about that. However, it would not allow the super-fast feeding behavior that results in the distant strobes known as quasars, which are believed to be such super-massive black holes below this limit.
Ultimately what they're suggesting is that quasars can't last forever because eventually their growth slows down to practically nothing, and then you have a relatively quiet, but huge black hole. Please keep in mind, however, that the end of the article disclaims this as being speculative physics. It makes sense, and it seems to fit the data, but it hasn't been thoroughly validated yet.