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."

Comments

Interesting repercussions

[AKAImBatman]

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.

Re:Interesting repercussions

[Zenaku]

I'm not an astrophysicist either, but as far as I can tell nothing about this hypothesis contradicts the idea that once matter crosses the event horizon it doesn't come out again, except as radiation. They aren't saying that the black hole begins "ejecting" gas, just that at that mass it gives off enough radiation to prevent any more gas from falling in.

I'm not sure I buy that as setting an upper limit on the size of a black hole. It just means the rate of growth would slow, and potentially reach equilibrium with regards to the surrounding gas. If something denser, like a star were to fall in, I doubt that the radiation pressure would push it away.

But who knows. I don't.

Re:Interesting repercussions

[jbeaupre]

Not quite sucking them in and spitting them out. Rather it's when the inflowing matter creates so much heat it clears out all the remaining matter in the area. Creates a "dry galaxy" (their term, not mine). So nothing left nearby for it to suck in and thereby grow.

An analogy would be how when a star forms it coalesces to a point that it produces enough energy to clear the area (T Tauri wind?). The star growth is then capped.

Re:Interesting repercussions

[KillerBob]

Side note: makes much more sense then the big bang theory, which reeks of creationism.

Until somebody asks where it all came from in the first place. Then you're back at square one, with the same problem that the Big Bang theory has.

Unless you adopt the Hindu/Buddhist take on the cosmology... it wasn't created, it didn't magically poof into existence out of nothing: it just is. Always has been, always will be, and goes through periodic cycles of growth and destruction, without end.

Re:Interesting repercussions

[Colonel Korn]

I'm not an astrophysicist either, but as far as I can tell nothing about this hypothesis contradicts the idea that once matter crosses the event horizon it doesn't come out again, except as radiation. They aren't saying that the black hole begins "ejecting" gas, just that at that mass it gives off enough radiation to prevent any more gas from falling in.

I'm not sure I buy that as setting an upper limit on the size of a black hole. It just means the rate of growth would slow, and potentially reach equilibrium with regards to the surrounding gas. If something denser, like a star were to fall in, I doubt that the radiation pressure would push it away.

But who knows. I don't.

You are completely correct. Good work.

Re:Interesting repercussions

[Ethanol-fueled]

Unless you adopt the Hindu/Buddhist take on the cosmology... it wasn't created, it didn't magically poof into existence out of nothing: it just is. Always has been, always will be, and goes through periodic cycles of growth and destruction, without end.

...and that's the explanation which makes the most sense to me. I like science to be mundane and predictable. If I want drama then I'll go see a movie and entertain the thought of some big magical guy in a toga who made the Earth with snot and space rocks.

Re:Interesting repercussions

[Bemopolis]

or 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.

What happens, roughly, is that stars that stray too close to the black hole are torn apart by the tidal forces, their constituent gas adding to a large torus of gas orbiting the black hole. Some fraction of this torus loses enough angular momentum to either fall into the event horizon of the black hole, lost "forever" (astronomically speaking), or a grazing collision that gives it enough energy to avoid being sucked in. This gas can form a galactic wind of sorts: that flow becomes collimated by the high spin rate of the black hole and the torus of gas around it. This produces jets like those seen emanating from the core of M87. That gas, with its high temperature and flow rate, will not cool to a low enough temperature to coalesce into new stars any time "soon" (astronomically speaking.)

Now, there are flows that involve gas being ejected from the disk of the galaxy with less energy, which can rain back down onto the disk and contribute to newly-formed stars. But these "champagne flows" are usully caused not by the energetics of the central black holes, but rather the collective stellar winds from the stars in the disk; for example, the galactic superwind of M82

In both cases, the thermal energy of the ejecta is insufficient to explain the gravitational anomalies you mention.

Re:Interesting repercussions

[Mr. McGibby]

Side note: makes much more sense then the big bang theory, which reeks of creationism.

So, instead of using rational thought and evidence to decide what theory is correct, you're going to use your "gut" feeling to make the determination? Sounds a little like what the relgionists, that you're so quick to deride, like to do.

Re:Interesting repercussions

[SBacks]

Why does everyone assume that nothingness is the default? From everything we've observed of the universe, it tends towards chaos and disorder (entropy). Nothingness is the complete lack of entropy, so why would should that be considered stable?

And, by the way, there are branches of cosmology that contend that the universe, has, in fact, always been and will always be. It comes from the idea that as you measure time further and further backwards, you find yourself measuring time forwards again. It has something to do with string theory, but the math is way beyond me.

Re:Interesting repercussions

[sexconker]

Don't feel bad, the physics is way beyond the string theorists, so they just make up the math as they go along.

Re:Interesting repercussions

[Mr. McGibby]

OK, read again. You still sound foolish.

Doesn't sound like an afterthought. Sounds like the whole point.

Re:Interesting repercussions

[interiot]

If something denser, like a star were to fall in, I doubt that the radiation pressure would push it away.

It's not just that it pushes gas away, it also gets to the point where it prevents star formation in its vicinity:

Furthermore, it appears that black holes can keep the gas too hot to settle in large quantities back to the galaxy's nucleus or to form stars through most of the galaxy's bulk. ... "So galaxies reach the point where you don't make stars."

But stars can still form elsewhere and be pulled in, yes. These black holes would be ~one tenth the mass of our galaxy, so they should be able to capture other galaxies that orbit it and eventually fall in.

Re:Interesting repercussions

[Visaris]

I came here to post almost the exact same thing. The story is about a limit to the size of black holes with respect to the ways the universe is expected to have developed. This is not a hard limit on the size but more of an equilibrium thing as the parent mentioned.

Think about this thought experiment:
One finds a black hole and shoots energy into it in the form of light in discrete sized packets or quanta. If the packets are put in faster than the natural blackbody radiation of the black whole releases energy through Hawking radiation, it will grow in size. Since the black body temperature of the hole decreases as it gets larger, it can grow in this way indefinitely. The larger it is, the softer it pushes outwards (w.r.t HR)...

The story is only really talking about matter/gas clouds, EM energy is an entirely different beast.

Re:Interesting repercussions

[cthulu_mt]

I have enough trouble with "dry counties"; the thought of a dry galaxy makes we want to weep.

Re:Interesting repercussions

[Anonymous Coward]

Lets see if we can clear some of this up for everyone...

When you have a black hole sucking in matter, that matter will start to get denser as it gets closer to the black hole. The larger the black hole the farther its gravitational influence and the more matter it can attract. As the matter falls in and gets denser its rotational momentum causes it to orbit. As this happens it starts to get quite close together and due to friction begins to heat up. Eventually it gets really really hot and expands as well as emitting high energy radiation. Once this reaches a critical point it overpowers the gravity of the black hole attracting said matter and starts blowing it back out.

Eventually this wind will be dissapated and will be inconsequencial on the scale of 100s of light years. Since galaxies are tens of thousands of LY across the intergalactic medium is not affected by this.

Again, this is not due to anything being emitted directly from the black hole, only the superheated matter falling into it.

Re:Interesting repercussions

[steelfood]

Or perhaps nothingness is a state of equilibrium.

Re:Interesting repercussions

[The Wooden Badger]

Great Scott!

Re:Interesting repercussions

[fireboy1919]

Do they always assume that? I've always heard the phrase "heat death of the universe," which doesn't imply nothing...exactly, but it would be close.

Thanks to almighty laws of thermodynamics, we could theoretically reach a point where every bit of matter has been broken down into mere energy, and every quantum of energy is so far away from every other quantum of energy that no interaction ever happens again - everything stays in the lowest possible energy state, at the lowest level of organization.

If you could suddenly teleport to that time in the future, what you'd see for light years in every direction would be nothing at all. Sure, there'd be *something* since energy can't be destroyed.

It just wouldn't be doing much...probably not enough to detect.

Re:Interesting repercussions

[Ambitwistor]

See here for what the heat death of the universe would be like.

Re:Interesting repercussions

[Ambitwistor]

I don't waste my time arguing with creationist nutjobs like arminw, but just for the sake of scientific accuracy, you should know that cosmological redshift is NOT quantized into discrete redshifts. The people who claim so don't even understand what "quantization" means.

In the past there has been some weak evidence of a periodicity in redshifts in small samples of galaxies. "Periodicity in redshift" means that galaxies are more likely to be found at multiples of certain redshifts than others. It does not mean that the redshifts are quantized, meaning they only occur in discrete multiples. Even if you accept the claimed periodicity, there are most certainly plenty of galaxies (the vast majority, in fact) which occur at redshifts other than periodic multiples.

The studies which purported to find periodicities didn't all agree with each other as to which redshifts were the peaks. That's a hallmark of data-mining a spurious signal out of noise, a classic outcome of small-sample statistics. When you take into account any of the following factors (1) large sample sizes (we now observe far more galaxies than when those original claims were made), (2) the existence of large scale structure (you're going to see more galaxies at certain distances if that's where a supergalactic cluster is located), (3) sample selection bias, the "effect" goes away.

You should also note that periodicities in redshift do not contradict the evidence in favor of the expansion of the universe, either. Even if they existed, the most direct interpretation is that there is inhomogeneous large scale structure formation (which we already know there is, see point 2 above).

Tens of billion?

[courteaudotbiz]

few tens of billion of solar masses

Since when "tens of billion" is "few"?

Re:Tens of billion?

[OglinTatas]

When your national debt is in the tens of trillions

Re:Tens of billion?

[Hatta]

So the phrase "astronomical numbers" is now superseded by "economical numbers".

Re:Tens of billion?

[eldavojohn]

When your national debt is in the tens of trillions

Stop spreading FUD, it's only a single ten of trillion.

Re:Tens of billion?

[megamerican]

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.

Re:Tens of billion?

[gv250]

There are 10^11 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers.
Richard Feynman, US educator & physicist (1918 - 1988)
http://www.quotationspage.com/quote/26930.html

Agreed, Very Interesting repercussions

[eldavojohn]

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.

Re:Agreed, Very Interesting repercussions

[Clandestine_Blaze]

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

What scares me unnaturally is the uncanny resemblance. We're doomed!

Re:Agreed, Very Interesting repercussions

[psychicninja]

As always, it brings up interesting questions about what was before that epoch...

The Sixties?

Re:Agreed, Very Interesting repercussions

[mcgrew]

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."

Microscopic singularities. Of course, the press wouldn't eat that up; newspapers don't exist to educate the public, they exist to generate revenue.

Re:Agreed, Very Interesting repercussions

[Ambitwistor]

Well, I'll admit this sounds intuitive with the Penrose-Hawking singularity theorems applied to the Big Bang.

No, it has nothing to do with singularities (or the Big Bang). It has more to do with matter which orbits black holes.

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.

Don't think of the singularity as a point that blew matter in all directions. As you correctly note, there is nothing "around" a singularity. For now limit consideration to an infinite universe, which is preferred by standard inflation scnearios. Then a singularity isn't even really a single point. The universe is still infinite in extent, it's just that the matter/energy in it is of infinite density. (See here.) Think of the Big Bang as where space expands making the matter less dense, rather than some single location that spews matter away from itself.

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).

To reiterate, this research has nothing to do with the singularity inside of black holes. It has to do with matter which is outside black holes not being able to make its way in, due to the pressure created by other infalling matter. The black hole itself does not emit any appreciable matter/radiation (other than a very tiny amount of Hawking radiation).

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.

I agree. "Micro black hole" is a terrible name. I prefer "Death, Tiny Destroyer of Worlds".

Re:Agreed, Very Interesting repercussions

[Fourier404]

It is questionable if it is acceptable to do so if they are end-term on a horrific disease, due to the chance of recovery.

The girl in India thought that she was at the end-term of humanity with zero chance of recovery. According to what she knew, even your definition makes her suicide acceptable.

Re:Agreed, Very Interesting repercussions

[aproposofwhat]

"if you can remember them, you probably weren't there"

Though after the shock news of myelin erosion increasing after the age of 39, most of us who were there are now struggling to remember...

Oh, and get off my lawn :P

Re:Agreed, Very Interesting repercussions

[aproposofwhat]

"Death, Tiny Destroyer of Worlds"

So that's a microVishnu, then?

Colliding black holes

[CubicleView]

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?

Re:What if our universe were one big black hole?

[elFarto the 2nd]

I saw an interesting interview with Michio Kaku here, and he talks about just this.

Just Like MRIs

[Anonymous Coward]

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.

Re:Just Like MRIs

[ppanon]

Ignoring the fact that non-profit groups might have the same reasons for cutting corners

It's less of an issue. For-profit corporations in the US are required by law to maximize profit for shareholders. Non-profits usually have different priorities. Sure there's still a lot of potential for individual greed gumming up the works, but non-profit organization eliminates a whole class of failure modes. For some types of enterprises, society is willing to accept the risk of those failure modes in exchange for the increased efficiency that they can provide in delivering a desired product. However a very strong argument can be made that the production of energy through nuclear fission has sufficiently bad potential consequences (thousands or millions dying and trillions' worth of land and resources unavailable for decades vs. a few thousand people out of work) that the greater efficiencies sometimes available through for-profit organizations are not worth the risk.

Stable Structure?

[corsec67]

What if there was a black hole, at this size limit, inside of a very dense cloud of gas?

Would it look like an enormous gas planet to an outside observer?
If the gas cloud was dense enough, could fusion start, creating a star with a hollow region between the "star" part and the black hole, held in place by this "radiation pressure"?

Hmm, what if the external part started becoming solid? Would it be like a planet, but inside out with "gravity" provided by the pressure from the black hole? Of course the radiation on the inside would be huge. Would the outside have tolerable gravity levels, due to the empty space inside?

Heh, I think I have one sentence there that isn't a question.

He's quoting Feynman-

[Petskull]

He's quoting Feynman:

"There are 10^11 stars in the galaxy. That used to be a huge number. But it's only a hundred billion. It's less than the national deficit! We used to call them astronomical numbers. Now we should call them economical numbers." -- Richard Feynman

Also: Economical Number
A number n is called an economical number if the number of digits in the prime factorization of n (including powers) uses fewer digits than the number of digits in n. The first few economical numbers are 125, 128, 243, 256, 343, 512, 625, 729, ... (Sloane's A046759). Pinch shows that, under a plausible hypothesis related to the twin prime conjecture, there are arbitrarily long sequences of consecutive economical numbers, and exhibits such a sequence of length nine starting at 1034429177995381247.
http://mathworld.wolfram.com/EconomicalNumber.html

No matter ejected from inside the hole

[iamlucky13]

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.

We need to find the ANCIENT TIME-LOOP DEVICE

[Joe The Dragon]

To control the loop.

Re:slashdot editor fail...

[kosack]

It's not totally crazy - when talking about black holes, the "size" of the black hole refers to it's Schwarzschild radius, which is directly proportional to its mass. Though you're probably right that in this case it's just a mistake!

Re:Where does the energy come from? Hmmm?

[Dan Ost]

Black holes do radiate particles (search for "hawking radiation" on Wikipedia), but that's not what they're talking about here. As matter falls into the black hole, it gets superheated and radiates lots of EM. Thus, it isn't radiation from the black hole that clears out the surrounding space, but radiation from the matter falling into the black hole.

Real limits on black holes

[ziani]

Personal experience has shown that black holes expand to about the size of a corporate accounting department.

They may actually be one and the same thing.

UPPER BOUNDS OF BLACKHOLE!

[Windows_NT]

Bill Gates found it in the 80's:
640K!