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

[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

[cthulu_mt]

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

Re:Interesting repercussions

[Ambitwistor]

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

Re:Tens of billion?

[OglinTatas]

When your national debt is in the tens of trillions

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

[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: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.

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: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

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.

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.

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!