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Space

Baby Black Hole With Big Appetite 170

Posted by timothy from the sucks-like-a-failed-relationship dept.
kuni ito writes: "'According to the astronomers who detected the object with Japan's Advanced Satellite for Cosmology and Astrophysics (ASCA), the black hole seems to be acting like a supermassive black hole, despite its size. It's sucking up matter at roughly the same rate as its much larger (and seemingly less hungry) relatives, they said.'" This black hole (assuming that black holes exist) seems to be eating a lot more than would otherwise be predicted.
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Baby Black Hole With Big Appetite

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  • They don't have infinite gravity. They just have to have enough mass-->gravity to overcome neutron pressure, about 2.4-2.8 solar masses or so.
  • Hate to be a nitpicker, but I'm pretty sure it's 4.7 light years approx.
  • They have neither infinite gravity nor inrinite mass. What they do have is a finite (but kindof large) mass in an extreamly (infinitely?) small volume. If a blackholes had infinite mass or gravity, there wouldn't be a universe as everything would have been sucked in a long time ago.

    Infinite mass -> infinite gravity -> nignificant (infinite?) gravity at infinite distance.

    Bill - aka taniwha
    --

  • And why are you mentioning special relativity?

    Mmmm.. maybe because normal relativity doesn't like black holes very much?

  • The Chandrasekhar limit is the mass over which a star's gravity can overcome electron degeneracy pressure. This pressure is a consequence of the exclusion principle, caused when electron waveforms are restricted.

    Any star greater than the limit, originally 1.4 suns (later recalculated to 1.2 suns), will collapse past white Dwarf stage to a SuperNova. What happens then depends again on the mass of the star, but that is not the Chandrasekhar Limit.
  • Excelent! Thanks very much.

    [please moderate this "me-too" into oblivion.]

    My .02
    Quux26

  • They also emit Hawking radiation which emits energy, thus, over time, black holes burn out.
  • Yes indeed, corpuscular was intended to illustrate a 19th century mentality of the concept of black holes (which originated in the 19th century). The concept was similar...that all 'corpuscles' of light escaping from said massive star strove against gravity so difficult that it turned aside and was rent back into its origin. Thereby, no light could escape such a massive star.

    Red shifting to infinity is what does occur to such photons, escaping from a schwarzchild radius as such. Red shifting of a photon increases it's wavelength while reducing the amount of energy that photon contains. Therefore, infinite redshifting means the photon has an infinite wavelength and contains no energy (thereby obeying the law that no information or energy can directly* leave a schwarzchild radius [the technical term used for Black Hole until BH was coined in the 60s]) So, a photon escapes from the black hole, but it doesn't really...exist, technically. Not easy to illustrate in a post here, I'm sorry.



    *directly being added after Hawkings theories of BH radiation
  • BOTH, Nerd is a very loosely used term, relateing to anyone who is excesivly skilled or obsessed in a particular area (Especialy those areas that the general public know little to nothing about.) Microft
  • Sorry, that's nonsense. No accelerator we can build has anywhere near enough energy to create a black hole. Probably would need one the size of the solar system.

    Stefan
  • Just some inline holes in stealth mode. Really, it's a black hole, how do we know if there's a huge black hole behind it or not? I think a black hole is just an ulcer in a huge stomach and once you get in, you wade around in the muck with all the other stuff that's been swallowed.
  • *dons asbestos suit, welder's mask* Can you imagine a Beowulf cluster of these things? *ducks*
  • A good popular account of things gravitational is Jayant Narlikar's The Lighter Side of Gravity [dannyreviews.com].

    Danny [danny.oz.au]

  • Actually, from what I've read, the time it would take for the black holes to completely consume everything was longer than the time it would take for the Universe to stop expanding and fall back into itself (the so-called Big Crunch).

    So, there's no need to fear being eaten alive by black holes billions of years in the future. Just watch out for all of the galaxies coming straight at you from every corner of the Universe. One word of advice: duck!

  • PreviousGuy wrote:
    "So, why isn't the "event horizon" (a distance from the actual point of the hole) a sphere extending the same radius in all directions?"

    You replied:
    "You can't "see" the event horizon. The event horizon is where light can no longer escape and by definition puts out no light. All you would see is a black hole in space -- hence the name "black hole." If you see something fall into a black hole, you would't see it actually hit the event horizon; it would merely keep falling in more and more slowly. In any case, the event horizon tends to be quite small. If you collapsed the Earth, for example, into a black hole, the event horizon would have a radius of just one inch. Only a supermassive black hole of millions or billions of solar masses (the kind you have at the center of big galaxies like the Milky Way) will have large event horizons."

    But the question is still a good one if you forgive the incorrect phrase of "see".

    Does a black hole exert it's force equally in all directions? I would imagine with such force that peturbations would be minor at best. If it is rotating, does the even horizon have an egg-like curvature as opposed to a beach-ball?

    This is stuff I've never thought about but would sure like to know now that someone brought it up.

    My .02
    Quux26

  • "This black hole (assuming that black holes exist) seems to be eating a lot more than would otherwise be predicted."

    Hmmmm... perhaps we should name it Sally Struthers?

  • Maybe more likely then just two passing strangers hooking up, is a galaxy which has two black holes in it's center like twin stars.

    With the size of the universe, and the probability of this happening. The chances are good that somewhere there existed, exists, or will exist a twin black hole.

  • No, I bet the N'Sync's songs would have a STRONGER sucking ability than the blackhole!

  • The report seems to be that this thing is eating more than a teenage BH should be. But given the way they eat (everything from light on down) wouldn't this just mean that it ran across a particularly dense "meal"?

    And because it's fairly fundamental to my Theory of Everything, do BHs grow as they eat?

    oh, and Space.com lost about forty points on my credibility scale with this link under the story

    "Aliens Among Us -- Which celebrity is really an alien? You decide! " [space.com]

    They trying to muscle in on the Weekly World News? [weeklyworldnews.com]
    --

  • a question (Score:1)

    by Anonymous Coward
    this may be a dumb question, maybe i should just go to bed, but anyway ..... if this small black hole is acting like a big black hole ... remember a while ago people were talking about that accellerator in NY that could possibly cause a small black hole ... if this is true, maybe even a tiny black hole like that one can kill us all... wee

    if you find this interesting, good for you, dont moderate me up, i posted a/c so people wont laugh at me, but if i get a score 5 or something ill be pissed, i want the karma damnit!
  • it could be 4.7. I kept getting parsecs in ly, AC's dist in ly, and AC's dist in parsecs confused when it comes to the tenths (I know it's 3.x, 4.x and 1.x, respectively).

    Bill - aka taniwha
    --

  • I'll help you with this one. Black holes don't have infinite mass, but the do have infinite density. That's probably where that 'infinite' probably wandered into your thinking.

    J
  • I agree... perhaps the amount of mass intaken by the hole is simply the amount of mass available? Excellent point/theory.
  • I can't remember the term for it off the top of my head, but as light is emitted by a massive object, it is redshifted a bit, where the amount of redshift corrolates with how massive the object is. Blackholes are merely massive enough to cause an effectively infinite redshift.
  • I have a quick, and possibly completely wrong hypothesis. According to Hawking (and PLEASE correct me if I'm wrong) that black holes evaporate, due to the creation of "virtual particles".

    Many physicists believe that a true vacuum cannot exist with any stability, and in the presence of a vacuum the universe gets cranky and (by taking a little local energy) fills the space with pairs of opposite and equal "virtual particles" which, while not quite real, have mass. Usually, these particles attract each other, and annhiliate.

    Now, our black hole, which is causing the local space to be subjected to fairly hard vaccum, spawns quite a few of these almost-particles. Some of these pairs are created across the event horizon. The poor particle inside is sucked into the singularity, while its lifemate is flung at extremely high speed out into the nothing. Through some trickery of conservation, this causes the black hole to lose mass, albeit at a rate much less that it is gaining mass.

    Here's where my hypothesis kicks in: a black hole that is more massive would have a larger gravity well, and thus a wider event horizon. Basically, it has more surface area. So there's a lot more area in which those v-particles can be torn from each other. Thus, it would evaporate faster. So a really massive black hole's "evaporation" rate would be much higher since surface area increases very quickly with increased volume.

    You're probably thinking that the mega-hole would pull mass in faster and would thus offset the evaporation rate. This is where my hypothesis gets a little threadbare, but lets explore a little anyway. First, the gravity well on the mega-hole is so huge that the angular escape velocity will be much lower than a midrange hole, therefore more of the local masses will be above the speed threshold of the gravity well, and ride the slingshot out into deep space, never having gotten near the event horizon. It would, if you are buying this, essentially be throwing its own food away.

    A second possibilty that could lower a mega-hole's mass aquisition is that since the mass near and beyonmd the event horizon is going to be getting increasingly dense in any black hole, there may be an upper velocity to how fast the hole can suck in more matter. Much like wind resistance keeps a skydiver from passing the speed of sound. Thus the black holes wouldn't have a linear increase in their rates of "easting" with respect to mass.

    So, our friendly neighborhood mega-hole would be evaporating much faster, eating a little faster, and throwing away a significant portion of the local produce. Sounds pretty inefficient. Anyone buy this?

  • Basically, what I was talking about doesn't have that much to do with the temperature of black holes or the evaporation of black holes.

    What you want to know about is Hawking Radiation, as this is actually related to both of your questions. I suggest you grab a copy of Stephen Hawking's A Brief History of Time and read on hawking radiation. If you could get a copy of the illustrated brief history of time, even better, as I've found that book easier to wade through. I'm not going to try to explain hawking radiation, as a physicist friend of mine (not from caltech) yelled at me that what I was saying about hawking radiation would confuse people. Besides, Professor Hawking is far more elegant than I am.

    Moller
  • Yes indeed, corpuscular was intended to illustrate a 19th century mentality of the concept of black holes (which originated in the 19th century). The concept was similar...that all 'corpuscles' of light escaping from said massive star strove against gravity so difficult that it turned aside and was rent back into its origin. Thereby, no light could escape such a massive star.


    Ok, thanks, makes sense now :-)

    And you did explain the red shifting more than enough for me to figure out what you're talking about. (and I knew who schwarzchild was too, ;-) )

    again, thanks.

    Moller
  • We must measure the size of black holes improperly... For example you can't measure a persons hieght and wieght by how much gas passes through the body. Same goes for black holes... Also don't you find it to be a bit racesist... BLACK hole... why not WHITE hole?????
  • I understand. The others answered my original question in addition to the question I knew not how to ask without knowing the answer .. anyways .. thanks for the response :-)
  • Great! Interestingly, I've had this book for a good number of years yet I forgot I had it! Thanks!!! :-)
  • I think black holes are THEORETICALLY infinitely zero in size and have infinitely high gravity. But, I think that's just because it worked out well in the math. If it had infinitely high gravity, everything would be moving toward it pretty damn fast.
  • We don't KNOW enough about black holes to say whether we could create a tiny black hole, though. We don't even know if they exist. Probably, the only way to protect ourselves from a tiny black hole destroying the earth like that, though, would be to figure out anti-gravity (if it exists) or some kind of gravity projector to cancel out the BH's gravity.
  • Thank you. In watching the Discovery or Learning Channel, such programs often do a good job of illustrating theory; however, it's not often that they go into greater details to the point where my questions can be answered .. books are good -- an answer.
  • What he may be talking about is a black hole having infinite density. Zero size, nonzero mass = divide by zero error.

  • Re:Hmm... (Score:3)

    by Hewligan ( 202585 ) on Wednesday August 30, 2000 @03:30AM (#817695)

    Okay, I'm gonna admit it - I am a physicist. At least that's what my degree says, anyway. I just though it might be helpful to explain what I got from it. Sadly, it the article was kinda lacking in details, but this is what I gathered.

    Basically, a black hole is a big old sucky thing. It pulls in everything around it. Since the stuff can only fall in so quickly, the stuff spends a lot of time whirling around the black hole before it falls in. While it's whirling around, it tends to bump into the other stuff that's similarly whirling.

    Now, with all that whirling and bumping, some of the stuff gets turned into x-rays (E=mc^2, remember?).

    Now, the stuff that got turned into x-rays doesn't make it into the black hole, which is useful 'cause that's how we detect the things in the first place.

    With a bigger black hole, there's a lot more whirling and bumping going on, so less of the stuff that the black hole starts out sucking on makes it into the Sarlac pit - I mean black hole (sorry, just re-watched ROTJ).

    That means that with a smaller black hole, a bigger proportion's gonna make it into the black hole itself.

    At least, that's what I got from the article. But then, my specialty's nuclear physics...

  • however, according to Einstein, the singularity has zero space (and, therefore infinite mass ... )

    Zero volume implies infinite density, not infinite mass...
    ___

  • What's the deal with the event horizon? All the pictures I've seen (admittedly, many from science-fiction) depict a circle, and stuff gets sucked through it like a gate, and funnels downward (so the circle becomes the base of a sort of curvy concave cone shape).

    So, why isn't the "event horizon" (a distance from the actual point of the hole) a sphere extending the same radius in all directions?

    I'm just guessing here, but could it have something to do with the accretion disk associated with a Kerr (rotating) black hole vs. A Scwartzchild (non-rotating) black hole? Or maybe I have that backwards. In any case, the visible stuff would be the material being sucked in, excited by radiation from the material as it is accelerated. Or something like that. Aren't black holes x-ray sources?

  • Okay, let's look at this concept of a 0 Kelvin mass.

    To have a temperature of 0 K, the object must have no kinetic energy (as temperature is just a function of the kinetic energy of the constituent particles). Now thermodynamics says you can't have a temp of 0 k, but thermodynamics is just a statistical thing, and only really works when you have a large number of particles. So let's look at something small. Start with an atom.

    An atom has a bunch of electrons going around it. If we take away the elctron's kinetic energy (withour magic KE sucker), they fall into the nucleus. They then bump into the protons, producing neutrons and energy, which means more KE to suck away.

    But let's keep on sucking. We suck away the KE from those neutrons. But, the exclusion principle says that they can't be in the same place at the same time. Well, that's an over-simplification. What it actually says is they can't have the same energy level. In other words, each of them must have a different enegy level to the others. In other words, only one of those neutrons can have an energy of 0.

    But wait, it gets worse. Those neutrons are made up of quarks. Two down quarks, and one up quark, in fact. Each of the down quarks, being the same type of particle have to have different energy levels. So we can only have one quark with a KE of 0. But we can't get a quark on its own.

    Since we can't get that one particle on its own, we can't get a KE of 0, so we can't get a temp of 0 K.

    There are, of course, other particles we could try this with, but no matter what we end up finding there is no such thing as a mass with a temp of 0 K.

    The simple fact is that entropy is just another measure of energy. The very idea of a mass without energy is nonsense, and that is why it is safe to say that a BH's radius is proportional to its entropy.

    Hope that helped, and I hope I didn't get too caught up in physics stuff.

  • I believe the first black hole we detected (again, assuming black holes exist), was Cygnus X-1 (or cygnus something), and we detected it by the x-rays it gave off.

    Yes, it was Cygnus X-1, but it's since been absorbed by RedHat V2.

    ;-)

  • I don't think we can say that the black hole is rotating. The singularity is a point with (effectively) zero volume, and I would say that this precludes it's ability to rotate.

    Since the singularity has zero volume, it must exert its gravitational force equally in all directions. Perturbations in a gravitational field would arise from unevenly distributed mass within a given volume. Since we have no volume, we can't have an uneven distribution of mass.

    Moller
  • How about, "You little asshole!!!!"
  • Now, with all that whirling and bumping, some of the stuff gets turned into x-rays...

    Um, that's not correct, is it? I thought that the stuff whirling around is whirling so fast that when it bumps into other stuff, the energy from momentum is what's being given off as x-rays. The stuff itself is not destroyed (converted into energy) but rather slowed down. Unless you're suggesting that there's nuclear fusion happening, which I suppose is possible.


    ...phil

  • ...is it lost forever?

    If you drop a copy of the WinNT source code into a black hole, will *all* copies of WinNT source code disappear? Ditto for Linux.

    Now, *that's* an OS war.

    Ref:

    http://math.ucr.edu/home/baez/physics/open_quest ions.html
  • ...that SIZE isn't everything. I've heard that one before, unfortunately from a few of my former girlfriends. Or could it be(here I digress because I just can't resist) that an asshole is an asshole, regardless of size? The fact is (I firmly believe after having subjected myself to a Master's Degree in math and many headaches at the U. of Chicago) that it's not a question of how much black holes "swallow", but how much they "produce"..., or create, if you will. We just don't know WHERE the product of their appetites manifests. There are some interesting theories on that, and I get back later with some Euro-links on the subject if anyone is interested. The question may be posed another way: After the theoritically anticipated "spaghettification" of matter and time that takes place when approaching a black hole, where oh where does the spaghetti go? "Why, it gets converted into energy.", seems to be the accepted and hopeful answer, but personally, I'm not so sure. This might be a phenomenon quite like the dimensional extension of the moebius strip..., the Klein Bottle: the curved "continum" turning in(or out) upon itself. But that's too simplist, I'm sure. And as for TIME itself......That really poses a problem... (I've got to go to work now)
  • Black Holes & Time Warps: Einstein's Outrageous Legacy [earthlink.net] by Kip Thorne. It goes into enough detail that you won't be left feeling empty, but it's well within the reach of most amateur enthusiasts.
  • The diameter of the event horizon of a black hole is proportional to its entropy. The entropy of a black hole grows as it accretes matter (this preserves the second law of thermodynamics). Thus the event horizon grows as the black hole eats. The event horizon is the point of no return- after you pass it there's no escaping from the black hole. We can't really look inside, but according to general relativity the actual singularity at the center of the hole has no actual size- it's just a point, sort of like an individual photon or electron.
  • As long as the people of 52001 have access to your witty and insightful comments, it will have been worth all the trouble.

    ---------///----------
    All generalizations are false.

  • I agree it might be just a dense part of space. And yes, the event horizen of black holes do grow as they get larger, however, according to Einstein, the singularity has zero space (and, therefore infinite mass, but... that's obviously not true or the entire universe would be pulled to a black hole (of course, there is the theory that the uiverse is a black hole... but that's a whole different thing)). And, if you believe Hawking, they also shrink as time goes on.


    Grades, Social Life, Sleep....Pick Two.
  • Now is not the time to be investing in blackhole IPOs, no matter how tempting their prospects for growth are. The market is simply too unstable.

  • Size matters? (Score:4)

    by kevlar ( 13509 ) on Tuesday August 29, 2000 @07:59PM (#817710)

    What I find interesting is how they say its a "small" black hole thats gobbling up "lots of stuff". Yet the only way we have of detecting black holes is through the amount of x-ray radiation that escapes at the poles, and heating of dust as it rotates and falls inward.

    A black hole that has contradictory data about its size would obviously point to the existence of a seperate unidentified object.
  • Shouldn't small black holes be MORE massive than big ones? I mean, the more matter a black hole collects, the more gravity is exerted on the matter, the smaller the hole gets. Am I missing something here?
  • I don't think we could all get more confused than that article left us, but let me try by asking a few questions:

    The article is trying to reveal something surprising, but which is it:

    That mid-mass black holes are just as INefficient as super-massive black holes, thus bringing an unexpected phenomenon into a new realm of scale?

    or

    That mid-mass black holes are just as powerful, and thus considerably MORE efficient than, super-massive black holes, thus limiting the odd inefficiency of super-massive black holes to only the highest mass scales?

    In any case, I don't think it means that the mid-mass black holes are inexplicably efficient.

    Some questions about the low-efficiency super-massive black holes:

    Doesn't the mass that gathers around these holes "dilute" the gravitation as you get closer to the black hole, and are surrounded by mass in all directions? Assuming this has been accounted for, how much more inefficient are these holes than expected?

    Could the supermassive black holes be decaying, thus weakening the rate at which new mass gathers, while still being surrounded with the mass and radiation to be expected from their large initial mass? Isn't decay a prediction of Hawking's?

    Lame-ass speculation is of course perfectly welcome in lieu of real answers...
  • Sorry about that, apparently I was miss guided by myself. Perhapse I should go move to a neutron star somewhere :)
  • are you some sort of idiot?

  • hawking's law extended (warning long) (Score:1)

    by Anonymous Coward
    this is an interesting article and some very good responses too. but to answer some questions.
    a black hole does not have infinite mass. You see mass is the amount of matter in an object. if it had infinite mass we wouldn't have a universe. Black holes have infinite density. it's so dense that 2 quarks end up existing in the same space at the same time. which is an impossibillity thus all matter is destroyed and a singularity where timespace its self does not exist and matter cannot exist occurs.

    however since the innitial mass of the black hole no longer exists the black hole does not gain mass even when it sucks up mass. instead all mass and energy entering a black hole is destroyed. now you're probably saying "wait matter and energy can't be destroyed" well the more up to day version is that the sum of matter and energy in the universe remains constant.
    and that matter can become energy and vice versa. this throws a big monkey wrench in the theory that the amounts of matter and anti matter chan remain the same. it comes out finally like this.
    the sum of matter, antimatter, and energy in the universe must remain constant.

    acording to hawking as matter falls into a black hole anti matter comes out. not that the matter is directly converted but rather it's the universe maintaining the ballance. antimatter is created at the point of destruction for matter to compensate for the universes loss of mass.

    further notes are thus. gravity is the opposing element to matter,antimatter and energy (we'll call them mass for short)
    wherever there is mass there is a directly proportional amount of gravity. it all stems from the beginning. imagin there is nothing.
    no mass
    no gravity
    in order to facillitate the creation of matter the universe borrows agains gravity. thus gravity is the debt which mass owes to creation to be paid back at the end of time in a big crunch. (you can read all about this in Hawking's black holes and baby universes)
    now back to black holes
    supermassive black holes do generate less gravity at the event horizon. it's even theorized that one could fly a craft into one big enough safely. that is untill you hit the singularity whereupon you're mass is destroyed and an equal amount of countermass is expelled to compensate.
    you could consider black holes as the universe's recycling center where all complex mass is replaced by simple mass.

    in a further note. all black holes eventually decay. you could call it the universe healing its self. they begin to expell more and more matter untill they've not only compensated for what they sucked in but also the original mass that they were born from and dissapear.
    like a giant algebreic equation all things are equal in the end. while I'm not that much of a mathmetition it does make sense.

    I really have no explaination as to why this black hole sucks up more than it's size allows for. but perhaps I've offered enough data here for everyone to formylate their own theory. I'll be putting one together too.

  • because as far as you are concerned, whatever you are watching falling into the black hole never actually falls into the black hole. Because of the time dilation that an object experiences as it falls into a black hole, we never see it actually fall into the black hole.

    To use an example from Stephen Hawking's A Brief History of Time:

    Suppose that you are watching an astronaut fall into a black hole. Suppose that you can see the watch on the astronaut's wrist. As the astronaut approaches the event horizon, the seconds will start ticking off slower and slower. Actually, each second will take twice as long as the one before, until finally, before the astronaut passes the even horizon, the last second on his watch will take an infinite amount of time to elapse (from your viewpoint). Of course, the astronaut notices none of this, and time passes normally for him as he flies through the event horizon to his death.

    This is a consequence of special relativity. In your reference frame (the observer's frame), the astronaut will never actually pass the event horizon. But, since the speed of light is equal in all reference frames, you can still see him because light is still reflecting off of him as far as your concerned.

    And the light doesn't grow "Dimmer" as you get closer to the event horizon. The light still has the same intensity, it isn't like the black hole is sucking photons off of their course out of light rays passing by, the event horizon is more like a "curtain", on one side light is passing normally (normally enough, it isn't slowing down, just "curving" because of the warping of space-time around the black hole), and on the other side of the event horizon, light spirals into the singularity, never to escape.

    Hope that elucidates things.

    Moller

  • Sorry if I gave the impression it's being destroyed. You're right, it's not and that's not what I meant. It's the bumping that produces X-rays, but that still means less energy for the BH to absorb.

    Hope that's clearer.

  • "I don't think we can say that the black hole is rotating. The singularity is a point with (effectively) zero volume, and I would say that this precludes it's ability to rotate."

    A previous poster noted that if the earth collapsed into a black hole then it would be about 1mm across - which is clearly not zero.

    As an aside, I think it's interesting to note how many people think that if our sun turned into a black hole that it would suck us in. Even when presented why this isn't so they still don't get it.

    My .02
    Quux26

  • Re:singularities and parallel universes (Score:3)

    by Claudius ( 32768 ) on Wednesday August 30, 2000 @04:43AM (#817719)
    From what I've read, a black hole is a singularity with mass. That is, it has mass but not size, it is a one-dimensional point. The only measurable property that a black hole has is mass.

    Perhaps you should try reading more on the subject, since you seem to be a bit mistaken on black holes' propertiese. For starters, black holes may have a net electric charge and (if magnetic monopoles exist) a net magnetic charge. They may have a net angular momentum as well. All of these, in principle, are observable from outside a black hole's event horizon.

    Furthermore, a black hole singularity does not need to be a single point. In the case of a charged, rotating black hole, for instance, the singularity is ring-shaped and has the curious feature that if you were to travel through the center of the ring it's anyone's guess where you would end up. You could, in principle, find yourself in a universe that is on a different "Riemann sheet" than the one we are in now that is connected to our universe through the little bridge of spacetime at the center of the ring singularity. Except for the untidiness of inevitably finding oneself inside a black hole's event horizon in the "parallel universe," this piece of physics seems tailor-made for science fiction.

    From a practical standpoint you are correct, however. In 99% of the problems in astrophysics nobody gives a hoot what the esoteric properties of a black hole are. It's just a compact critter that radiates x-rays like crazy when it gobbles up matter. (A notable exception to this is people who study accretion in quasars, where assuming a Kerr geometry instead of a Schwartzchild geometry can affect accretion models by a noticeable amount).
  • Maybe he means two black holes that just happen to be in the same spot in the sky but at vastly different distances ?
  • Call Reed Richards... sounds like Galactus is in the area.

  • This is nonsense. Perfect Black Holes can't exist, and the event horizon cannot be passed, since for all outside observers, everything that happens near the event horizon happens like infinitely slow, so nothing ever hits the black hole.
  • Black holes can be detected (in theory of course) by looking for the emissions they give off. The theory goes (extremely roughly) that as individual particles reach the "edge" (event horizon?) of the black hole (crossing this line means you never come back), some of them are torn apart, half of the particle going in, half going out, and some energy is released during this fission. It is these fissions at the edge that make a black hole appear to give off energy, and make it detectable.

    That type of radiation is called Hawking Radiation (after Stephen Hawking, naturally). However, this isn't what lets us detect black holes, as Hawking Radiation is ridiculously faint. Black holes can be detected by the X-Rays that they "inadvertantly" produce. When matter is falling into a black hole it is accelerated, heated, and compressed to such a degree that it gives off large amounts of X-Rays. I believe the first black hole we detected (again, assuming black holes exist), was Cygnus X-1 (or cygnus something), and we detected it by the x-rays it gave off.

    Another method of detecting black holes is to look for graviational lensing effects. Because black holes are so massive, they bend the fabric of space time. (Imagine a sheet suspended in the air. Place marbles on the sheet. The marbles make depressions on the sheet, like stars make "depressions" in space-time. A black hole is so heavy, it's like dropping something that is the size of a marble but with the weight of a bowling ball onto the sheet. The sheet bends A LOT, and it actually will have a hole where the singularity is.) Light travels in a straight line, so if space-time curves, light also curves with space-time. Gravitational lensing was proved during a solar eclipse. Astronomers observing the eclipse noted that they were able to see stars that should have been blocked by the eclipsed sun. The sun's gravitational field caused enough "lensing" so that stars directly behind the star could be seen to either side of the star. So, if we find something out in space that is causing a LARGE amount of gravitational lensing, but we can't see anything, there's a chance it's a black hole. At that point we normally observe it more to determine if it is or isn't a black hole.

    Moller
  • IANAAstronomer, but I do remember reading that for smaller black holes vs. bigger ones, the gravitational increase after passing the event horizon is curves up much more quickly for small holes vs. big ones (with gravity on the y axis and time on the x, I believe).

    Not sure if this has anything to do with how much matter is being consumed by a smaller black hole, however?
  • When the hell did this happen?

    ....ok im a dork...
  • Or... tidal forces are much larger around a smaller black hole, could this have anything to do with it?

    That was my first knee-jerk thought, but it's silly if you think about it. Tidal forces don't help you pull the matter in any faster. They just make things more painful for the object being sucked in.
  • A previous poster noted that if the earth collapsed into a black hole then it would be about 1mm across - which is clearly not zero.

    No. The Event Horizon would be about 1 mm across. The singularity has a finite mass with zero volume. That is the definition of a singularity.

    Moller
  • Light doesnt spiral down into the singularity, that is a very corpuscular way of approaching the issue. light actually redshifts to infinite and therefore its energy ceases to exist..

    Also, I think the interpretation of the 'stationary observer' from hawkings book is being mis-construed; a stationary observer does not exist, and therefore it is a theoretical arguement illustrating the effects of spacetime shifting from the gravitational warping of the black hole.
  • I don't think we can say that the black hole is rotating. The singularity is a point with (effectively) zero volume, and I would say that this precludes it's ability to rotate.

    Rotating black holes have singularities that are not point-shaped, but rather are one-dimensional, ring-shaped beasts. As such they can have an angular momentum. IIRC (and it's been a decade since I've studied GR) the rotating nature of the black hole singularity distorts spacetime around it and causes reference frames to be "dragged" around the black hole. This is odd since it leads to a component of the gravitational force that appears to observers at large distances from the black hole to be "sideways" from the direction one would expect from Newtonian physics. ("Preposition overload" is a problem endemic to talking about GR).
  • IIRC, Hawking radiation deals more with the evaporation of very small black holes. This explains why there are no microscopic black holes, as they should have been formed in the Big Bang, but we dont detect any because they have 'evaporated' over billions of years. Hawking radiation does not appreciably affect the mass of black holes formed by collapsing stars, which is how most black holes are formed.

    IANAAP (Astro-Physicist)
  • From what I've read, a black hole is a singularity with mass. That is, it has mass but not size, it is a one-dimensional point. The only measurable property that a black hole has is mass.
  • Twin black holes rotating around one another would produce a lot of noticeable effects.

    First, you would see a very funny-looking accretion disk and some very strange radiation patterns.

    You'd see massive Doppler shifting from the x-ray spouts, not unlike our observations of the binary pulsar in (I think) 1974.

    Black holes wouldn't rotate around each other for long -- in their case, the gravitational radiation would be enormous, causing the system to radiate energy away until they collapsed into one another.

    Finally, no wrinkles to special relativity. Gravity's pull would relate to general relativity.

  • 10^70 to eradiate a black hole 3 diameters of our planet. BTW. for all the protons in the Universe to decay it's only 10^30 so we will never see a black hole eradiate since all the matter will decay way before that time

  • BLACK HOLE LINKS (Score:4)

    by SynchroSmitty ( 160503 ) on Tuesday August 29, 2000 @08:43PM (#817765)
    i think that was a poorly written and rather confusing article. for those of you who are interested, here are some links with better, more concise information on black holes. unfortunately i couldn't find anything better on the black hole in NGC 9345

    Black Holes and Beyond [uiuc.edu]

    Black Holes: Mystery of the Cosmos [intothecosmos.com]

    Black Hole: The Death of a Star [thinkquest.org]

    Shit Load of Links [lycos.com]

  • What's the deal with the event horizon? All the pictures I've seen (admittedly, many from science-fiction) depict a circle, and stuff gets sucked through it like a gate, and funnels downward (so the circle becomes the base of a sort of curvy concave cone shape).

    That's the accretion disk that is being depicted. The accretion disk is a vortex of matter that is spiraling into the black hole, getting ionized, energized, and putting out a lot of x-rays along the way. That's why sci-fi artists love to show the accretion disk. You can have a lot of fun and make it look really cool.

    So, why isn't the "event horizon" (a distance from the actual point of the hole) a sphere extending the same radius in all directions?

    You can't "see" the event horizon. The event horizon is where light can no longer escape and by definition puts out no light. All you would see is a black hole in space -- hence the name "black hole." If you see something fall into a black hole, you would't see it actually hit the event horizon; it would merely keep falling in more and more slowly.

    In any case, the event horizon tends to be quite small. If you collapsed the Earth, for example, into a black hole, the event horizon would have a radius of just one inch. Only a supermassive black hole of millions or billions of solar masses (the kind you have at the center of big galaxies like the Milky Way) will have large event horizons.

  • Name the hole (Score:5)

    by Felipe Hoffa ( 141801 ) on Tuesday August 29, 2000 @07:13PM (#817775) Homepage Journal

    Bill Gates would be a suitable name for it.

    Fh

  • that certainly sucks!

    *ducks*


    What do I do, when it seems I relate to Judas more than You?

  • I'm no astrophysics major, but here it goes...If these things are sucking up so much matter, do they not become more massive, and thus have even more gravitational pull? Basically, are they getting stronger as time passes? Do black holes in general get stronger? I consider myself an astronomy guy, but I'm afraid my knowledge of black hole theory is limited to how we detect them (provided, of course, they are what we think they are).

  • Yes . . . but you shouldn't think of a Black Hole as a drain hole in the universe. You should think of it the same way as a star, just without the light.

    If our sun collapsed in to a Black Hole instantly. The lights would go out, but otherwise the planets would continue to orbit. The planets would not stop orbiting and get sucked in.

  • Now, this is mainly just from my understanding of black holes having read Hawking's Brief History of Time and taken one astronomy course. But I don't remember ever reading about the light redshifting to infinite (if you could explain that in more detail for me, I'd be grateful).

    Perhaps he or she just meant that the light would redshift beyond the visible spectrum into the infrared range?

    And I'm not sure how you're using "corpuscular," I've never heard it used that way. ;-)

    That surprised me at first too. So I checked Noah [sourceforge.net] and it turns out that corpuscular can be used to refer to a stream of particles. The poster's infinite redshift idea would probably treat light as a wave instead of as a stream of particles. Thanks to quantum mechanics, both views are valid.

  • Oh oh... (Score:3)

    by Greyfox ( 87712 ) on Tuesday August 29, 2000 @10:55PM (#817794) Homepage Journal
    The sims have noticed the garbage collectors and will soon start correlating disrepencies they cause with the simulated physics of the simulation. Once they realize that they're just a computer simulation, they always commit mass suicide. Oh well. Time to reset the simulation and start a fresh run...

  • Re:Will black hole grow infinitely? (Score:3)

    by maxwells_deamon ( 221474 ) on Wednesday August 30, 2000 @12:00AM (#817801) Homepage
    Been a while since I have looked at this stuff so I may be a bit out of date on things. I have a physics degree but it is almost 20 years old and I don't use it. It is also a little late here so this is a bit rough.

    When a star is formed, mass comes together and starts hydrogen fusion. As the fuel gets burned up, the light pressure/heat is decreased and it cools and becomes more compact. It can stop at this stage, or go on to burn helium, (which requires more mass and pressure) if the right amount of mass is present, the gravitational pressure will squeeze the atoms into one big mass of neutrons. If even greater, the neutrons will be squeezed down into something and the mass will collaspe to become a black hole.

    A black hole is created when the gravitational force is increased to the point that light can not escape from the interior of the object. We don't care about the size of the mass at this point, it is the size of the radius of no escape.

    As you get farther from an object its gravitational effect is reduced. based on the mass and assuming the object does not spin, the size is directly related to the amount of mass. This distance is known as the event horizon.

    If an object is nearby, it is pulled toward the black hole. If it is going directly toward the BH it will cross the horizon and be effectively lost. except they add to the gravitation of the object as a whole. If it is close but moving at an angle, it is accelerated past the object, torn apart, squeezed in next to other objects, and heated till it emits X-Rays. This loss of energy may be enough to drop it into the BH. If it is far enough away the object falls into a stable orbit.

    Black holes generally grow in size. In a pure vaccume they can decay by the capture of 1/2 of virtual partical pairs. This happens at an increasing speed as the BH gets smaller.

    I belive that particles falling into a black hole will cross the last bit of the boundry and avoid the general relativity problems by one of two methods. Quantum tunneling, and sitting at the border long enough for the event horizon to grow past them.

    we can know very little about the inside of a BH because we can not observe then up close. Because they have been detected we do know that gravity can still exist inside them and the matter can have an effect still. (until they were detected I was betting that they would eliminate themselves as the gravity {space curvature} would not be able to escape)

    the size of a black hole can be estimated by three means that I am aware of. 1} stuff rotating around it (dopplar shifts and such). 2} Amount of stuff being taken in (not in this case) 3) rate of change method. *if an object has consistant changes that occur in a short period of time, that time can not be less than the time it takes light to cross the object*. (this is my guess as to the tool being used here)

    Despite all this I belive that it is possible to conduct some research into the interior structure of a black hole. {you must be a member of an advanced space traveling civilization of course}. just send two black holes at each other at various angles. momentum should be conserved. do they go through each other if they bump head on? What if they just touch? Send small black holes at a larger one and probe to determine the size of the nucleus just like Rutherford did with atoms. *The atom was unfathomable and unbrakeable until people started doing nasty things to it*

    There, that will give them something to fight about for a while ;-)

    I want a spell checker in slash dot :-(

  • uh oh... (Score:5)

    by Legolas-Greenleaf ( 181449 ) on Tuesday August 29, 2000 @07:21PM (#817804)
    It would suck (no pun intended, as it has been overused already in this story) if this ate the KEO time capsule [slashdot.org] before the future people of 52001 could get 20k copies of the decss code, erotic stories about Natlie Portman, copies of N'Sync's greatest "songs", and other historical momentos of our great civilization...
    -leoglas

    i've looked at love from both sides now. from win and lose, and still somehow...

  • Don't they exist? (Score:3)

    by Andrew Dvorak ( 95538 ) on Tuesday August 29, 2000 @07:27PM (#817807)

    Ok, I suppose a lot of good questions offer more than a lot of poorly researched replies to the original article.. So here's to being productive!

    Let me know if i am correct: Why is it that black holes cannot be detected? Is it because any light that would otherwise escape indicating its presence is consumed?

    Also: What are some good books on black holes that one of a mind uneducated as far as black holes are concerned might be able to read wiht little trouble?


  • Ummm, am I mistaken in remembering that a black hole has infitine mass?

    Also, the article says ~50k * Solar mass, which is definitely finite.
  • Beta Centauri is not part of the Alpha Centauri triplet. There is Alpha Centauri A & B (both G type iirc), and Proxima Centauri (M? red dwarf iirc).

    All three stars are approximately 4.2 (? can't remember that tenths digit) light years away with PC being a fraction of a light year closer (for now, anyway:)

    I want to go there (Alhpa Centauri)

    Bill - aka taniwha
    --

  • Actually, you are mistaken. A black hole has a definite, measurable mass. If it had infinite mass, it would have infinite energy and infinite gravity, and such a thing cannot exist in our universe.

    IIRC correctly, black holes instead have infinite density. This is not a contradiction, because the actual size of a black hole is zero (not the size of the event horizon, but the size of the actual black hole).

  • some of them are torn apart, half of the particle going in, half going out, and some energy is released during this fission. It is these fissions at the edge that make a black hole appear to give off energy, and make it detectable.

    Actually, Hawking radiation doesn't occur when particles are torn apart. Rather what happens is that one particle in a virtual particle/antiparticle pair is captured and the other particle leaves.

    Basically, particles and their antiparticles appear all the time out of nothing but disappear just as quickly (actually, the time the pair exists is inversely proportional to the mass of the pair). If the pair appears near the event horizon sometimes one of the pair gets caught and this prevents the pair from rejoining and disappearing. The net effect of this is to make the energy/mass in the visible universe seem to increase. This is a big no-no in physics so instead of that occuring, people believe that the blackhole loses enough mass/energy to balance out the creation of the particle. This basically implies that if a black hole doesn't have any matter around it to suck in, the black hole gradually loses energy due to Hawking radiation and at some point disappears.

  • My infinity is bigger than yours... (Score:3)

    by alienmole ( 15522 ) on Wednesday August 30, 2000 @12:12AM (#817814)
    As has been pointed out, black holes have neither infinite mass nor infinite gravity; just enough mass, compacted in a small enough volume, that light (or anything else) which penetrates the "event horizon" cannot escape. IOW, the "escape velocity" of a black hole is greater than the speed of light.

    As a matter of interest, you referred to the concept of a "value of infinite that is greater than other black holes". This has little to do with black holes, but it's worth noting that in number theory, there are indeed infinities that are bigger than other infinities. The proof of this is fairly easy to understand - if you're interested, try this page [mathacademy.com] for a very accessible explanation.

  • Ah!

    Is this how they explain the temperature of a black hole? A small one has a close event horison, so infalling matter orbits faster and faster (due to conservation of angular momentum), thus producing hot cyclotron radiation, while heavy holes have large event horisons, so matter doesn't orbit very quickly before it falls beyond the horison?

    But how does this explain evaporation of holes, which seems to happen w/o any infalling matter?

    Also (completely unrelated) Given a sufficiently heavy hole (where sufficient means the event horison is distant enought to not imply huge tidal forces) would it be possible for infalling matter to become trapped in orbit inside the horison?

  • It's really more well-defined to talk about the event horizon as being the boundary of the black hole. In this context, it makes sense to talk about the density of a black hole in the usual sense -- and in fact, this leads to some interesting (and perhaps non-intuitive) results. A classic for-instance : the density of a black hole actually drops as you crank the mass up. That is, supermassive black holes are much, much less dense than stellar-size ones. (And the tidal forces near the event horizon are much, much smaller -- so you could, in theory, take a spaceship and cruise very close to the event horizon of a supermassive BH without being ripped into shreds by the tidal forces.)

    Just so ya know. ;-)

  • There have been some good replies to this already, but hey! clarify, clarify, clarify.

    Re: formation. When a star is in the happy, go-lucky stages of its life (the Main Sequence, when its burning Hydrogen into Helium in its core), and even a little later, its structure is set largely by the balance of gravity against ordinary gas pressure. (Take the term "ordinary" loosely here.) Later on, as material in the core of the star becomes very tightly packed, etc, that core becomes electron degenerate -- what's holding it up is the tendency of electrons to dislike rather intensely being crammed next to other electrons. (Again, I'm grossly simplifying things here, but what the hell.) This, in turn, leads to all kinds of interesting things -- for one, the conductivity of electron-degenerate matter is extremely high, so it tends to be largely isothermal; for another, degenerate matter is just plain weird : when you pile more mass onto the degenerate core, the damn thing gets smaller! So you see the normal cycle of compression-expansion is screwed up, and strange things can happen. The degeneracy will actually be broken multiple times in the life of the star, as the core eventually reaches its ignition temperate (in massive enough stars : and remember, because its isothermal, the whole thing reaches the ignition temp. more or less at the same time -- which is why you get the so-called "Helium flash" or "carbon flash").

    I've veering wildly off-topic here, so back to the point: eventually, if the star is massive enough, even electron degeneracy pressure isn't enough to hold up the star against the crushing pull of gravity. The core collapses -- the electrons fuse with protons to form a big soup of neutrons, which can exert an even more impressive form of degeneracy pressure. (The core-collapse process, as you might imagine, is pretty dramatic: remember that this is an awful lot of mass we're talking about here. There is a rebound off the neutron-degenerate core, plus an outgoing flood of neutrinos which were produced in the p-e fusion into neutrons -- a truly stupendous amount of energy is released, and we call it a Supernova.) And (you can probably see this coming) if the remnant core is massive enough, even neutron degeneracy pressure isn't enough. But we know of no force in the universe that can stop the collapse after that : the object collapses indefinitely, to a singularity.

    But the Black Hole, it should be mentioned, comes into being long before all the mass is concentrated in a single point : a BH can be said to exist the moment an event horizon exists -- that is, the instant the density of matter in a region is so great that the escape velocity from that region is greater than the speed of light.

    God, that was a long answer to a short question. To top it all off, the supermassive BHs in the cores of galaxies may be totally different beasts -- nobody is entirely sure how they form, though certainly there is a long process of merging and growing before they attain their current (billion-M_sun) masses.

    2.3.4 : I don't really have the energy to answer these very completely anymore. :-) But very "briefly." 2: black holes don't suck, any more than normal matter does. If our sun were magically replaced by a black hole, our orbit wouldn't change one bit. (Of course, we wouldn't have too long to appreciate that fact, since we would miss rather dearly the lack of sunlight.) A BH is "different" from a normal object, attraction-wise, only once you get pretty darn close to the thing. So yes, they will eventually stop growing. 3: people use "size" sloppily, but I usually mean the radius of the event horizon. This is really the only definable radius for a BH; it is related to the mass by a well-known formula. Some people also use "size" interchangeably with "mass" -- there are certainly more or less massive BHs. 4: no. :-) but you're actually hitting on some real points here -- to an outside observer, and supposing certain other things, it would like someone falling into a BH was taking an infinite amount of time to do so; in fact the Russian term for BHs was, IIRC, "frozen star," for precisely this reason. read Kip Thorne's book, called -- I think -- "Black Holes and Time Warps," for a good discussion of this sort of thing.

    Hope this helps.

  • OK, my claim to insight is that my partner was fourth author on this paper and I used to be an astronomer - but don't let either of those fool you into believing I know what I am talking about....

    What the article doesn't explain very well is that this is the (or one of the?) smallest BH found. There has been a lot of speculation that small galaxies contained small BHs, but that they didn't emit X-Rays because they didn't accrete matter. But NGC4395 shows that they do (well, at least one does).

    As far as efficiency goes - it's not very efficient (less efficient than many (most? all?) of the supermassive BHs), but more efficient than would be expected if "all" small galaxies had small BHs like this (otherwise you'd see a lot more emission from small galaxies).

    Does that make sense? The important point is that they have detected emission from a small BH, which means that earlier *speculation* about small, non-emitting, BH in other small galaxies has to be re-thought.

    More info is here [unisci.com]

    On your other points:

    For a spherically symmetric distribution of matter, gravity is *not* "diluted" by an outer shell. If you are inside an isolated hollow shell, for example, there is no gravitation field from the shell (if you are near one side then the pull from the close stuff is equally balanced from the larger amount, but more distant, remainder of the shell to the other side of you).

    And, if I remember correctly, Hawking radiation is a tiny effect. It is insignificant compared to the accretion rate for any BH that is visible - it's only important once the BH has accreted everything and is floating around in empty space by itself.

  • Translation of article based on original paper (Score:5)

    by alienmole ( 15522 ) on Wednesday August 30, 2000 @01:01AM (#817824)
    From reading the actual paper [arxiv.org] on which the space.com article was based, I think I've figured out the real point. As I understand it:

    Many low luminosity galaxies, although showing evidence of having very massive black holes at their center, appear less bright than expected given the calculated size of their black holes. This has been explained by models which assume that the black holes in question are "underfed", i.e. that there's no longer enough matter close enough to the holes to create larger amounts of radiation.

    However, the galaxy described in this paper, NGC4395, is an exception to this scenario, which is why it is interesting. Although it is of similar low luminosity to the galaxies described above, according to this paper, it shows evidence of containing a much smaller black hole than other low-luminosity galaxies. This smaller hole is from 10,000 to 100,000 solar masses, which is small for a galactic-core black hole.

    The paper concludes that NGC4395 behaves more like a brighter galaxy with a larger hole, but because its hole is small, it appears dimmer. Attempting to apply the massive-underfed-hole model to this galaxy, based on it having low luminosity, gives incorrect results; instead, the model that applies is that of brighter galaxies with larger holes, except that in this case, the hole is smaller and thus the galaxy dimmer.

    The space.com article actually did manage to say something along these lines, but you have to completely ignore the first half of the article, which is confused nonsense, and read the following paragraphs:

    Until now, scientists had speculated that black holes residing in galaxies with dim cores - such as NGC 4395 - were either too old or too small to quickly eat up lots of material, as more massive black holes do on a regular basis. But now it seems that "mid-mass" black holes (a new nickname for the smallest type of supermassive black holes) may simply be more efficient matter-eaters.

    "We now see that the nuclear source in NGC 4395 is a scaled-down version of black holes found in the most luminous of galaxies," said, Andrew Fabian, another Institute of Astronomy researcher who worked on the discovery. "Everything is the same, only it is smaller."

    As a result, some astronomers now think that the total output of X-rays from accreting matter may therefore be more a product of how massive the black hole is, rather than of the luminosity of the region surrounding the black hole, as it once was thought.

  • Hawking and Berkenstein came up with this concept in the 70s. Since Hawking radiation implies that black holes have a temperature it follows that they have an entropy as well, and the relationship is S=A/4h, where A is the surface area in appropriate units.

    This theory has recently been proved using string theory. Since entropy has its basis in the number of available quantum states of a system, Strominger and Vafa showed this relationship to be true by counting the degeneracy of configurations for strings and D-branes corresponding to black holes in string theory. This is a real result for string theory, since up till then the theory only had a semiclassical derivation.

    For more information, see here [ucsb.edu] for more information on the superstring proof or here [aol.com] for the semiclassical derivation.

  • Yes, I think they determined its mass (about 50.000 sun masses) by observing its effect on the galaxy it sits in. I don't think it has a larger gravitational pull than other black holes of the same mass - if it had, it would look like a larger supermassive black hole of several million sun masses. If I understood the article right, this BH gobbles up mass at the same rate as a black hole of millions of sun masses. Matter falling into a BH is accelerated by the gravitational pull to tremendous speeds and is heated up to very high temperatures. You cannot see the black hole itself, but matter falling into it is very visible - especially in the x-ray spectrum.

    I think, this particualar black hole swallows so much matter, because there is enough matter there. Most supermassive black holes probably already have consumed most matter in their vincinity.

    Stefan
  • I by even further means would be an astrophysicist, but if a blackhole had infinite mass let's say.

    Lets not say that, because they don't have infinite mass ;-).

    The article even says 50k * solar mass.
  • Let me know if i am correct: Why is it that black holes cannot be detected? Is it because any light that would otherwise escape indicating its presence is consumed?

    Very, very, good question, but actually reading the article yields:

    Black holes are regions of space so dense, not even light can escape their gravitational pull. As a black hole gobbles up gas, dust and even entire stars, the incoming matter gets so hot, it gives off high-energy radiation as it plunges into the hole. This energy includes X-rays, which are detectable by telescopes in near-Earth orbit.

  • why? because: (Score:3)

    by Captain Pillbug ( 12523 ) on Tuesday August 29, 2000 @07:34PM (#817829)
    There'd be an enormous observable doppler effect. Two blackholes rotating around each other (besides being improbable) would have to revolve at an enormous speed in order to avoid collapsing from their enormous gravitational pulls.

    And why are you mentioning special relativity? Special relativity is all about not taking gravity into account, and blackholes are all about gravity.
  • Black holes do get "stronger" as they accumulate more mass. However, Stephen Hawking has shown that black holes also radiate energy. This implies that black holes, if not "fed" with mass, will disappear given time.

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