Forgot your password?
typodupeerror
Space Science

Black Holes May Not Grow Beyond Certain Limit 201

Posted by ScuttleMonkey
from the stand-back-I-don't-know-how-big-it's-gonna-get dept.
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."
This discussion has been archived. No new comments can be posted.

Black Holes May Not Grow Beyond Certain Limit

Comments Filter:
  • by AKAImBatman (238306) * <akaimbatman @ g m a i l . c om> on Monday October 27, 2008 @02:20PM (#25530927) Homepage Journal

    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* [amazon.com] 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.

    • by eldavojohn (898314) * <.moc.liamg. .ta. .nhojovadle.> on Monday October 27, 2008 @02:28PM (#25531031) Journal

      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 [wikipedia.org]. 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 [wikipedia.org] 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: (Score:3, Funny)

        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. [kuvaton.com] We're doomed!

      • Just Like MRIs (Score:5, Interesting)

        by Anonymous Coward on Monday October 27, 2008 @02:58PM (#25531495)

        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.

      • by psychicninja (1150351) on Monday October 27, 2008 @03:12PM (#25531659)

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

        The Sixties?

        • XD Wish I had mod points
        • Re: (Score:3, Funny)

          "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

      • by mcgrew (92797) * on Monday October 27, 2008 @03:16PM (#25531729) Homepage Journal

        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.

      • by HTH NE1 (675604)

        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."

        Bugophants [amazon.com]?

        Actually, in that book they don't evaporate and never stop eating, but they do send information back in time commensurate with their size.

      • by Ambitwistor (1041236) on Monday October 27, 2008 @05:14PM (#25533449)

        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 [ucla.edu].) 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".

    • They get sucked in, crushed, then ejected as gassous emmisions which then collect and reform as a new star.

      That sounds a lot like the big bounce [wikipedia.org] theory, which is like the big bang except that the bounces are periodic. It depends on the theory that space begins to behave repulsively as the amount of mass packed into it reaches a critical point.

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

      • by KillerBob (217953) on Monday October 27, 2008 @02:40PM (#25531233)

        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.

        • by Ethanol-fueled (1125189) on Monday October 27, 2008 @02:46PM (#25531329) Homepage Journal

          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.

        • by SBacks (1286786) on Monday October 27, 2008 @03:06PM (#25531593)

          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.

        • by rrohbeck (944847)

          Those Hindus may not be far off:
          http://www.sciam.com/article.cfm?id=big-bang-or-big-bounce [sciam.com]

        • Always has been, always will be, and goes through periodic cycles of growth and destruction, without end

          So overall you're a steady-state cosmologist. I assume you were quite perturbed by the emergence of Big Bang Theory?

        • by bonch (38532)

          "It just is" sounds like a halt in the pursuit of answers.

      • by Mr. McGibby (41471) on Monday October 27, 2008 @03:02PM (#25531541) Homepage Journal

        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.

        • 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.

          The 100 trillion life forms that reside in my gut have faith in my ability to provide for them, why should I not listen to their prayers?

          More than 500 different species of bacteria exist in our bodies, making up more than 100 trillion cells.
          http://www.brainsturbator.com/art [brainsturbator.com]

    • by Zenaku (821866) on Monday October 27, 2008 @02:34PM (#25531131)

      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: (Score:3, Informative)

        by Colonel Korn (1258968)

        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: (Score:3, Interesting)

        by interiot (50685)

        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

      • Re: (Score:3, Insightful)

        by Visaris (553352)
        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
        • Regarding your thought experiment: the cosmic microwave background radiation is a much larger influx than the Hawking radiation outflux of any stellar (or larger) black hole. So unless the black hole is isolated from the rest of the universe, it will always grow from cosmic radiation, even if no matter falls in. (Or at least until the universe expands enough that the background radiation becomes cooler than Hawking radiation; see here [ucr.edu], in the second half.)

        • by blair1q (305137)

          "EM energy is an entirely different beast."

          No it isn't.

          The reason a black hole has an event horizon is that it has gravity. The reason it has gravity is that it has mass. If shooting energy into it can grow it, then shooting energy into it increases its mass.

          But what if it doesn't? What if it just increases its temperature?

          Then the black hole can increase its rate of radiating energy. Which will at some point repel particles and preven the accretion of further mass.

          Increasing temperature can also increa

      • Bill Gates found it in the 80's:
        640K!
      • If something denser, like a star were to fall in, I doubt that the radiation pressure would push it away.

        True, but that star falling in would increase the output of radiation (how permanent would that increase be?), and make a little bit harder for the next one to fall in. Eventually even the stars would be pushed away, and you'd have to step up to feeding it neutron stars (and eventually, other black holes). At least that's how I understand it.

      • by nschubach (922175)

        What if the matter isn't entering the "event horizon" but is being shot out like a projectile from the other side and in doing so causes other object near it to follow? There are whole galaxies like this, but what if you looked at them from the "top"? Would they "look" like a black hole?

    • by jbeaupre (752124) on Monday October 27, 2008 @02:40PM (#25531227)

      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.

    • by Bemopolis (698691) on Monday October 27, 2008 @02:51PM (#25531403)

      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 [nasa.gov]. 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 [nasa.gov]

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

    • by iamlucky13 (795185) on Monday October 27, 2008 @03:32PM (#25531935)
      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 [nasa.gov].

      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: (Score:2, Insightful)

      by 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 we

  • by courteaudotbiz (1191083) on Monday October 27, 2008 @02:22PM (#25530949) Homepage

    few tens of billion of solar masses

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

  • Thats nice to know, another less thing I have to worry about!
  • Clearly they've never been to goatse.
    • by Tatisimo (1061320)
      Goatse is more like a virus than anything else. Once you are goatsed, you must goatse others. Goatse shold be studied by biologists, not cosmologists.
  • by CubicleView (910143) on Monday October 27, 2008 @02:52PM (#25531415) Journal
    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?
    • by corsec67 (627446)

      Or would the black holes repel each other, possibly leading to clusters of black holes like The Maw [wikia.com]?

    • by Urkki (668283)

      This "limit" is just a practical limit. If this is correct, then it's just very hard to feed a lot of mass to thig big a black hole, because if you try to feed it too much, it'll blow away most of the mass you were trying to get in. So considering the age of the universe, and the mechanisms by which they accrete matter, you get a max size for the biggest black hole possible.

      But if you merged two such black holes, you'd probably get a much bigger black hole, and there would be no limit. Or if there was a lim

  • Stable Structure? (Score:3, Interesting)

    by corsec67 (627446) on Monday October 27, 2008 @02:59PM (#25531515) Homepage Journal

    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.

    • by ceoyoyo (59147)

      It would look like a very dense cloud of gas first being turned into a rapidly rotating disc, heating up enormously, then being shot out in jets, from the poles.

  • Does something like this throw the Big Crunch (and cyclical universe by extension) out the window?
    • No. No amount of pressure can prevent a collapsing universe from collapsing; that's the content of various cosmological singularity theorems. This doesn't even prevent simple things like galaxies colliding. It really only works because a black hole event horizon is relatively small, and it's hard for a lot of matter to all cram in. But in a collapsing universe, once you get to the point that things are starting to collide, the collapse has already built up enough that it's unstoppable. Past a certain p

  • not so fast! (Score:2, Interesting)

    by Lord Ender (156273)

    You can test these theories like you test software. Consider an edge case.

    Suppose there exist two of these "maximum" density black holes on a collision course. Sure, the "radiation pressure" may exceed gravity at some point for low-momentum gas particles, but that doesn't mean the pressure would be so much greater than gravity that it would halt an oncoming super black hole (with corresponding super momentum!).

    It seems in such a scenario it would be possible to form a black hole with double the "maximum" ma

    • by ceoyoyo (59147)

      The paper (not the summary) doesn't suggest that you can't have bigger black holes, just that you generally won't because the normal way black holes grow has limits.

      Note that anything that's not actually another black hole will get torn apart by tidal effects, and two 30 billion sun mass black holes colliding is likely to be a fairly uncommon event.

  • the maximum size a black hole may reach is only few tens of billion of solar masses

    Physics understanding fail! Volume != Mass

    • Re: (Score:3, Informative)

      by kosack (155278)

      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!

    • by ceoyoyo (59147)

      For black holes "volume" (as far as that term applies) is strictly related to mass. Note also that "size" does not necessarily imply "volume," particularly for objects like black holes.

  • The energy to blow away the dust and gas from the black hole comes from infalling dust and gas. In the absence of infalling dust and gas the black hole doesn't emit any energy at all. So once it reaches this limit, and clears out the nearby vicinity of the hole, what keeps its neighborhood clear? It's no longer taking in matter, the radiation pressure drops, and the expelled matter eventually returns to start te growth again, no?

    This all sounds like the T-Tauri stage in stellar evolution... except that the

    • Re: (Score:3, Interesting)

      by Dan Ost (415913)

      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.

      • by argent (18001)

        Black holes do radiate particles (search for "hawking radiation" on Wikipedia)

        The hawking radiation from a galactic sized black hole is negligible.

        As matter falls into the black hole, it gets superheated and radiates lots of EM.

        Indeed, that's my point. One the black hole has cleared its surroundings to the point where it's no longer growing, then the radiation emitted from this source will drop until it starts growing again.

        • by Urkki (668283)

          Indeed, that's my point. One the black hole has cleared its surroundings to the point where it's no longer growing, then the radiation emitted from this source will drop until it starts growing again.

          But the expelled matter doesn't magically fall back. The matter that didn't fall in was forced into a stable orbit around the galactic center by the radiation pressure. There'd be only random wandering stars that by chance get too close to the central black hole in their orbits. But even a galactic black hole is a tiny tiny dot in the center of a galaxy, so these unlucky stars would be few and far between.

          So in practice the black hole stops growing in a galactic environment. It could grow if it got some ma

          • by argent (18001)

            But the expelled matter doesn't magically fall back.

            It's not magic, it's just turbulence. "Orbits" in a galaxy aren't ever going to be stable over cosmological time scales... and the ring outside the empty zone is still the densest part of the galaxy. It's going to spread out and flatten until the average density around the black hole starts increasing again, no?

  • The proposed situation does not forbid the growth of black holes, it merely suspects that the usual supply of material may be lost. Basically, the infalling material may become so energetic that it explodes outward and pushes away the interstellar dust and gas. However, anything which gets close enough to the black hole will still be pulled in. Growth of the black hole is not forbidden. Gas and dust which escapes "nearby" stars will still fall in, as will any stars which pass too near. The proposed mec
  • 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.

  • After the discovery that all galaxies had a super massive black holes at their cores, it was obvious that black holes had an upper size limit, since there are no universe spanning super galaxies.

    The discovery is about the mechanism of this fact, not the fact itself.

  • Farscape covered this at the end. Just ask John Crichton.

  • What if two black holes converge? Then I bet it would be one giant super black hole of death.

  • What if there is no gas? What if just one lollipop drops into the black hole every hundred years? Would the black hole then reach a limit "No more lollipops, please" ?

    Oh well,

    Stephan

It's a poor workman who blames his tools.

Working...