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Space Science

Hidden Black Holes Discovered 224

Posted by Zonk from the i'm-being-sneaky dept.
mknewman wrote to mention a Space.com article discussing the discovery of a large group of hidden black holes. From the article:"Black holes cannot be seen directly, because they trap light and anything else that gets too close. But astronomers infer their presence by noting the behavior of material nearby: gas is superheated and accelerated to a significant fraction of light-speed just before it is consumed. The activity releases X-rays that escape the black hole's clutches and reveal its presence. "
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Hidden Black Holes Discovered More

Hidden Black Holes Discovered

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  • Kessel Run (Score:2, Funny)

    by Xac ( 841406 )
    They found the Kessel system. http://www.atombender.de/swgwiki/index.php/Kessel_ System [atombender.de]

  • chicken and egg.. (Score:5, Interesting)

    by rd4tech ( 711615 ) * on Sunday August 07, 2005 @12:39AM (#13262339)
    what was there when it all started: galaxy or a black hole? [space.com]
  • OK, can one of you physics geeks explain to me why x-rays are able to escape the gravitational clutches of a black hole when light cannot? I've never understood this.
    • I think they don't really escape the black hole per se. They're just very high-frequency/high-energy radiation that leaves the super-heated gas BEFORE it 'falls over' the event horizon.

    • Re:Geek explanation required. (Score:5, Informative)

      by gardyloo ( 512791 ) on Sunday August 07, 2005 @12:48AM (#13262366)
      Light and x-rays are the same things (as you imply), just at differing frequencies. Visible light can escape from outside black holes' event horizons, just as easily as x-rays.
            Any electrical charge undergoing an acceleration emits radiation, if it can couple to its environment. Charges which are accelerated more emit radiation at higher frequencies, and accelerations near a black hole's event horizon are very large, so x-rays are emitted preferentially over visible light. There is also an effect of higher frequency emissions from any finitely-sized source being more "focused" than lower frequencies. This leads to more concentrated "beams" of emission from finite sources.
              Finally, one of the methods of radiation from black holes is that of spontaneous particle-antiparticle production in the tremendous gravitational gradient outside a black hole. Normally, these particle-antiparticle pairs recombine quickly. However, if one travels nearer a black hole than the other (they're emitted going in opposite directions relative to their center of mass, to combine linear momentum), it can get sucked down the gravity well, and the other escapes.

      • Re:Geek explanation required. (Score:5, Informative)

        by gardyloo ( 512791 ) on Sunday August 07, 2005 @12:55AM (#13262394)
        I forgot to mention one of the most imporant effects: matter which is around a black hole tends to form accretion disks. It forms disks because it tends to have a net angular momentum about the black hole's center, and so spins. The fact that differing parts of the accretion disk move at different speeds means that there is a lot of rubbing going on -- not unlike with slashdot readers. This leads to heating of the accretion disk, often up to a very high temperature; the accretion disk is just like a very hot oven, which doesn't emit (much) in the visible region, but a lot in the x-ray region of the spectrum. There are also tremendous focusing effects of magnetic field lines (accelerating charges again), and so the emitted radiation tends to get focused along opposing "jets".
        • So a black hole is like nature's garberator, and it's a good thing our solar system isn't charted to become part of one of their accretion disks?
          • Some would argue that our solar system very much IS charted to become part of the accretion disk at the center of our galaxy. Now that won't happen until after the sun burns up all of it's fuel, but you have to keep the big picture in mind when you get afraid of the small stuff ;)
      • Why is it that an electron orbiting the hydrogen atom doesn't accelerate? Acceleration into a different dimension - i.e. perpendicularly - is still acceleration, and normal electrons going circularly in a cyclotron do radiate. Yeah, it would mean an energy catastrophe, sooner or later it would have to give up juice, either potential or kinetic energy, and run out of it. So these day we just say - postulate - that it goes in circles but it's forbidden to accelerate thus radiate, but could we say "it doesn't
        • Although I don't necessarily think that your wording was very accurate, you've essentially hit one of the nails of strangeness in quantum mechanics quite squarely on the head.
          One of the reasons that it took Bohr so long to come up with the (admittedly extremely simple) orbital model of the atom is that, hey, charges should radiate extremely fast at those accelerations (based on all sorts of measurements, most notably by Rutherford), and all matter should basically collapse very quickly. He ev
          • Perhaps you could tackle your idea of "undergoing acceleration." After all, based on the correspondence principle, when you're inside an elevator, you have no clue whether you are sitting in a gravity field, or you're "undergoing acceleration." I'm asking for some kind of intuitive understanding of the structure of space, why inertial reference frames don't matter - Galileo's flies don't accumulate in the back of the ship, because they get tired trying to keep up with it, you don't feel motion - but as soon
        • This is the classical "white death" of the universe predicted by classical physics. An electron in a hydrogen orbital does go in circles. But it can only radiate to a lower energy state. As it becomes more localized around the proton, the uncertainty in position goes down and the uncertainty in momentum goes up. The electron eventually "floats" on this uncertainty in momentum, since radiating more photons does not get rid of it and can only increase it. This process is what forbids further radiative transit
      • Incidentally, my statement about finite-sized sources and "focusing" of radiations from it is correct... only not in this case (as far as I know). The beam formation from finite sources is due to monophase (or almost-monophase) emissions, and this sort of thing can't be expected from a black hole, even accounting for the finite speed of light. Mea culpa.

      • Finally, one of the methods of radiation from black holes is that of spontaneous particle-antiparticle production in the tremendous gravitational gradient outside a black hole. Normally, these particle-antiparticle pairs recombine quickly. However, if one travels nearer a black hole than the other (they're emitted going in opposite directions relative to their center of mass, to combine linear momentum), it can get sucked down the gravity well, and the other escapes.

        So there are anti-particles being e

    • Those X-rays don't "escape" the black hole because they aren't coming from inside the black hole. The idea is that as stuff falls into the black hole, it gets ripped apart at the atomic level. As it gets ripped apart, it emits x-rays. Because the matter hasn't quite reached the event horizon yet when this starts to happen, these x-rays are able to make it away from the black hole.

      So in other words those x-rays aren't coming from the black hole. They're coming from just outside the black hole, the dying scre

    • Re:Geek explanation required. (Score:4, Informative)

      by drxray ( 839725 ) on Sunday August 07, 2005 @12:58AM (#13262404) Homepage
      Nothing can escape from "inside" a black hole, from within inside the event horizon. But as matter falls into the black hole it heats up, the gravitational potential energy gets turned into heat through friction-type processes (this also happens in waterfalls, the bottom is warmer). Hot stuff glows, and the gravity near a black hole is so strong that the matter does not just get red or white hot, it gets X-ray hot. And a lot of the X-rays, since they're generated outside the event horizon but still very near the black hole, escape so we can see them.

      Most stuff doesn't generate much in the way of X-rays, so it's very easy to pick out the X-rays coming from the quasar. That's not so true of visible light - no doubt visible light also escapes from right next to the black hole, but it's drowned out by the outer regions of the quasar (which are visible-light hot instead of X-ray hot) and the galaxy the quasar is in.
      • Very nice explanation. You've read up on your ancestry?

      • Re:Geek explanation required. (Score:4, Informative)

        by The_Wilschon ( 782534 ) on Sunday August 07, 2005 @01:36AM (#13262506) Homepage
        Wrong in part.

        The X rays emitted have essentially nothing to do with the heat of matter falling in, and everything to do with acceleration of charged particles. In fact, it'd be nearly impossible to actually get any substance "xray hot" as you put it.

        When you heat a substance, it radiates, of course. This occurs due to electrons changing energy levels. These energy levels are very precisely defined, and thus the emission spectrum consists of sharp lines (they are not perfectly sharp due to perturbations like spin-orbit coupling, etc.). Then, in a macroscopic situation, many of the emitted photons will scatter off of other atoms, losing some energy in the process. By this mechanism, the sharp spectral lines get very blurred, and we see an essentially continuous spectrum (as long as you restrict it to middle range frequencies) with bright lines at the spectral emission frequencies.

        The reason that this process doesn't produce xrays, no matter how hot you get the substance is that the energy levels an electron could be in do not range from 0 to infinity. In fact, in the case of a hydrogen atom, suppose we take an electron in the lowest energy shell to have 0 potential energy. Well then, now we move that electron to an infinite distance from the proton. At this point, it will have lost ~13.6 electron volts of energy. Thus, the highest energy photon that a hydrogen atom can emit due to an electron changing energy levels is just 13.6 eV. This falls in the ultraviolet range. And then, by scattering off other atoms, photons only lose energy, rather than gaining it.

        Now, strictly speaking, as we increase the nuclear size, the difference in the energy levels will increase, and the energy of the emitted photons will be higher. So, if we used heavy enough elements, we could conceivably get them "xray hot". But by that point, we would very likely have reached the ultra-unstable elements that have only been created for very brief periods of time in the lab before decaying. Obviously, these are not found in great quantity in nature.

        So, now that we know that heat isn't the culprit, how do we get xrays from black holes?

        Well, I could be mistaken, and if so, I hope someone less mistaken than me happens on this post to correct me, but I believe that it primarily occurs because first, the atoms are ripped apart by tidal forces (they are "spaghettified"), leaving the electrons and the nuclei separated. Then, obviously, these particles are accelerating, and accelerating charged particles generates electromagnetic radiation. The greater the acceleration, the higher the frequency of the radiation generated. And since the gravitational force of the black hole increases as you get closer, the acceleration will proceed at a higher and higher rate, so the frequency of emitted radiation from one individual particle should slide upwards. Of course, that doesn't take into account gravitational redshifting, so perhaps the two effects cancel each other out nicely, leaving us with xrays.
        • They're right.
        • Well, this is silly: ...if we used heavy enough elements, we could conceivably get them "xray hot". But by that point, we would very likely have reached the ultra-unstable elements that have only been created for very brief periods of time in the lab before decaying.

          The lowest electronic energy level goes like Z, and X-rays start at about 100 eV. So you could easily get a soft X-ray out of something as small as oxygen or neon, which while not common are hardly the unstable transuranics you're talking about
          • The lowest electronic energy level goes like Z, and X-rays start at about 100 eV. So you could easily get a soft X-ray out of something as small as oxygen or neon, which while not common are hardly the unstable transuranics you're talking about.

            True. I failed to bother to figure out what atomic number it takes to start radiating x-rays. However, it is still true that anything much heavier than hydrogen or helium does not account for much of the mass falling into most black holes. Additionally, in orde
        • Well, that was my explanation for 16 year olds, it glosses over a lot. Quadraginta is entirely right that there are plenty of emission lines from atoms and ions in the X-ray band - neutral iron for instance is at 6.4 keV (kilo-electron-volts) which is quite a high-energy X-ray.
          You're quite right that atomic emission isn't the whole story, emission from plasma (seperated electrons and nuclei) often dominates the spectrum. This emits by synchrotron radiation, Compton up-scattering of ultraviolet light from fu
      • Nothing can escape from "inside" a black hole, from within inside the event horizon.

        This is not entirely correct. For all intents and purposes, you are right, but.... this covers a bit of the "Information Paradox" [newscientist.com] surrounding black holes, and Hawkings' admission that he was wrong - information DOES escape from a black hole - eventually.
      • Nothing can escape from Heaven either. However, listen to the following story:

        St. Peter goes opens the gates of Heaven, because someone is knocking. A guy stands there, says "Aaaaa..." and puff, disappears, like magic. St. Peter doesn't understand it, he just shrugs his shoulders, closes the door back, and goes on his business. Soon, there is knocking again. Same thing all over, same guy there, about to say "Aaaa.." and puff, disappears again. This repeats a few times, until St. Peter loses his temper, and
        • "6549AD: Tourist trips to the depths black hole #XX9...Roundrip fare only $9999.999 denars."

          So, if I put a penny in the bank now, and resist spending it until then, I will be able to afford to go?
    • If you look at Einstein's (or Newton's even) equations for gravitation, you'll see that it is an inverse square law. This means that the further away you are from an object, the weaker the gravitational force is. Indeed, if you move twice as far away from an object, the force is four times weaker.

      Black holes have an associated event horizon. This is more or less the closest light can get without being sucked in. Obviously, the force of gravity is monumentally strong here. It is stronger still inside.

    • OK, can one of you physics geeks explain to me why x-rays are able to escape the gravitational clutches of a black hole when light cannot? I've never understood this.

      Those x-rays you're seeing are coming from hot gas outside the event horizon. Undoubtedly much more radiation is emitted inside it than outside, but any photon inside the horizon has a world-line ending at the singularity and not your eye. And the photons you do see have lost a lot of energy in the trip up from the horizon's edge. They could ha
    • It is NOT due to heat, or friction, or any sort of thermal radiation. Hydrogen (the most common thing approaching a black hole, and due to tidal forces, anything larger would get ripped apart anyway (the hydrogen gets ripped apart too)) simply cannot ever emit radiation of that frequency due to thermal effects. The highest frequency thermal radiation of hydrogen is in the ultraviolet, nowhere near xrays. Furthermore, due to redshifting, the actual frequency emitted in the hydrogen atom's frame of referen
      • http://vega.bac.pku.edu.cn/~wuxb/nstar.html [pku.edu.cn]

        The problem with your reasoning is that high magnetic fields (and, yes, this is one reason that perfectly spherical -- without net angular momentum -- black holes are basically impossible) really screw up the 13.6eV ionization energy for atomic hydrogen. In fact, strong enough magnetic fields (and you easily get them near black holes) raise the ionization energy of atomic hydrogen well into the thermal x-ray range.
    • There are two reasons why you would see x-rays from a black hole.

      The first source and most obvious to the observer is that they don't come from the black hole at all, but rather the accretion disk of hot gas around the black hole. As the accretion disk is heated by the black hole (as it approaches) all wavelengths of light are given off, x-rays being one of the "last" based on the spectra.

      The second source of x-rays is from what is called Hawking Radiation, named after Stephen Hawking. Hawking Radiation i
    • I'm not going to bother detailing the rest, as others have already answered this thoroughly.
      What I will add however is that saying that only X-rays escape is a total mistament.

      The rays escaping the Black hole's event horizon (basically the critical radius which is considered radius of no return) escape constantly. However, because of the gravitational strength of the black hole, the photons are redshifted. A redshift means their frequency is lowered. Their speed does not slow down, but their frequency is le
  • Here's a Journal entry [slashdot.org] about previously unseen quasars (black holes, really) that was found by Spitzer, just by looking for infra red signatures instead of X-ray.

  • Nanoscule Macroscopes (Score:3, Interesting)

    by Doc Ruby ( 173196 ) on Sunday August 07, 2005 @12:42AM (#13262351) Homepage Journal
    Black holes bend space in every direction. Their effect on space is strongest closest to them, especially within their event horizon. But they bend all of spacetime, in every dimension, infinitely. At least to the distance in lightyears of the duration since their forming, and even before, when their spread-out mass still bent space, just not all in one place, and without the counter-intuitive effects within the event horizon.

    So it seems that relying on detectors which detect only the behavior of light between the Earthly observer and the unobstructed black hole is pretty crude. How long before we have nanodetectors that detect the miniscule (nanoscule?) deflection of a laser within a small space on Earth, away from the "straight" path we'd expect from the influence of the space matter that we can see? Maybe we have to account for the "dark" matter also bending space in the Universe. But such a detector seems like a lot more reliable mapping instrument, for all these cosmic masses, than just waiting for some gas to drift across the view of our traditional scopes. How long until we can start to use really sophisticated Einsteinian relativity detectors?
    • There is no ``dark matter'' (i.e. exotic matter) and ``dark energy'' seems unlikely.
      • Actually... dark energy is one of the hottest fields in physics right now... I'd sure like to see the source for your statements.
        • I thought Dark Energy/matter was like UFOs. A self limiting field: as soon as you know what something is, it's not unidentified any more. For instance, you can't be abducted by a UFO, because then you'd know what it is and it wouldn't be a UFO anymore.
          • Not really. It is not just being unidentified that makes it "dark", it really is dark. We can estimate from large scale observation of various cosmological trends (not sure exactly how, cosmology and astronomy are not my fields) how much matter/energy is in the universe. We can also count up how much matter we can see (because it is luminous, like stars or quasars). The two numbers don't match up. Not even remotely. The latter is something like 30% of the former. So, we conclude that there is a great
        • Dark energy is one explanation for certain observations (e.g. apparent increased acceleration at great distances). Certain string theories/M-theories offer alternative explanations for these observations; the correct theory may be completely different from string theory or dark energy. Right now dark energy is a "shot in the dark" which happens to be popular. It might be correct; everyone loves the cosmological constant. Although it has flaws, this Wikipedia article [wikipedia.org] contains some information. I hope tha
          • Yes, I do know the difference between a hot field and something which eventually turns out to be accepted theory.

            And no, I don't think that being a hot field would mean that there were no flaws. In fact, if there were no flaws, it would far more likely be what is known as a dead field, at least when it comes to theory. Experimentalists could still be checking it for ages, of course.

            The OP claimed dark matter and dark energy were dead fields already due not to them being absolutely correct, but due to
    • When we're talking about the miniscule types of deflections you're hoping to detect, things like the size of individual atoms start to get in the way. To detect things far away, you need macroscale detectors, not nanoscale. For some observations we use the orbit of the Earth itself to expand the size of a virtual detector.
      • I suppose the inverse square law means that a black hole's effect on a given nearby space is b/d^2, where b is the black hole's mass, and d is the distance to its center. While a nearby object, even an atom, has the effect a/n^2, where a is the nearby object's mass (and d is the distance to its center). So if b/a > d^2/n^2, the black hole has greater effect. How far is the nearest black hole, in Astronomical Units? And how many times, say, does it mass than the Sun? Better yet, how about its mass compare

        • Re:Nanoscule Macroscopes (Score:4, Informative)

          by syntaxglitch ( 889367 ) on Sunday August 07, 2005 @02:29AM (#13262653)
          Better yet, how about its mass compared to the Moon, and how many AU is the Moon from the Earth?

          Think of it this way:

          Most black holes are for obvious reasons of stellar mass, i.e, less than 20 times the mass of our sun. 20 AU doesn't even get you out of this star system--Pluto is 30 AU or so out. So the contribution of those black holes is going to be completely swamped by the sun.

          The supermassive black hole at the center of the Milky Way is thought to be in the neighborhood of a 10^6 solar masses; the galactic center lies about 2x10^9 AU in the general direction of Sagittarius, so any contribution from it will also be swamped by the sun.

          Nothing outside our solar system is likely to have any measureable gravitational effect on anything inside it other than the entire system orbiting the galactic center.
          • Because if it _had_, your solar system wouldnt be stable...

            The "bending" the greatparent speaks of is nothing mor than the normal workings of gravity... it wont be _any_ different from a star with a black hole from a ly away. Only closer than a stars radius it will be prominent, because of the singular nature of a black hole. Outside nothing will change.

            The only way we can hope to detect those "bendings" are when stuff _really_ gets hot, i.e. creation of black holes. The gravity waves should momentarily be
        • I was referring to the distance of deflection, assuming that our detector's finest level of resolution would be limited to the distance across an atom. Also assuming that we could detect a change in energy level from one atom to the next, and somehow compensate for normal spontaneous motion of the atoms.

          As for the other concerns about swamping gravity readings with nearby stars and other objects, I would say that your idea has a chance of working if you can find some way to focus, reflect, or shield from gr
    • you're talking about mapping the activity of an olympic sized swimming full chock-full of kindergardeners from the observations of a bobbing cork. There is way too much affecting it to factor out the individual stimuli.
      • I dunno, it's too hard for me and my Pentium4 with its desktop calculator. But is it too hard for the latest supercomputer, and NASA's astrophysics software team, with ringers from MIT, CalTech and maybe CERN, or their local brain tank?
        • If it were possible, do you think we'd still be using telescopes to find new planets?
          • In fact, we've been finding new planets in our own solar system through gravitational deflection since Pluto was "Planet X". And we continue to find distant stars and other objects through gravitational deflection. While our computing power, and further articulations of Relativity, grow faster than we apply them to astrophysics. Yet we also use telescopes to find new planets. In short, "yes".
            • Doc Ruby: Sorry but you are in error. For hundreds of years, scientists have speculated about the existence of additional planets based on perturbations, etc. in the orbits of observed planets but the discovery of a planet required direct observation. There is lots of indirect evidence for solar and extrasolar planets (plus the direct observation of some, perhaps all, solar planets). We find perturbations in luminosity, etc. and hope this indicates the existence of a planet. This article [asu.edu], last revised
              • The only "direct" observation of a planet is that of Earth: by smell, taste and touch our bodies directly experience molecules of the planet directly. Even the Moon we experience only indirectly: reflected sunlight, tidal effects on our seas. With the exception of extremely rare, tiny moon rocks that have dumped the gap, and of course the direct experience of the handful of astronauts who have felt the lunar surface through the deformations of their thick spacesuits.

                Optical confirmation of other planets, wh

    • "How long before we have nanodetectors that detect the miniscule (nanoscule?) deflection of a laser within a small space on Earth, away from the "straight" path we'd expect from the influence of the space matter that we can see?"

      Maybe not that long, but we will need a very long time to wait for our laser to pass by the black hole, reflect somewhere and come back to Earth.

      • " within a small space on Earth "

        The gravity from the black holes has already reached the Earth. Why send out the lasers to them, when we can watch the lasers twist through spacetime already bent nearby?

  • ouch (Score:5, Funny)

    by cente ( 785332 ) on Sunday August 07, 2005 @12:44AM (#13262354)
    Gee, doesn't that make you feel oh-so-safe for our upcoming space travel (many lifetimes ahead of us)... "a large group of hidden black holes." pot holes of the universe? You think driving is bad *now*...
  • astronomers infer their presence by noting the behavior of material nearby: gas is superheated and accelerated to a significant fraction of light-speed just before it is consumed.

    ...whereas gas is superheated and accelerated to a significant fraction of light-speed just before it is expelled from your average CowboyNeal.
  • It'll probably just turn out to be specks of grit on the scanner-scope.
  • Can anyone explain if the curent theories still speculate that eventually all the matter in the universe will be sucked up by black holes?

    Also, once that happens will the black holes (as the only remaining objects in spacetime) start attracting each other? I'm hoping they don't reach some sort of a gravitational status-quo where our universe just becomes a universe of complacent singularities.

    Nothing better to think about at 1:30 am on a Sunday morning than the death of the universe...

    • In a 'cold death' scenario, where gravity is too weak to pull the expanding universe back together (this seems to be the majority opinion, and people even talk about the expansion accelerating), I've heard the final distribution of matter estimated at: 9% black holes, 90% dead stars, and 1% dust and gas at 1030 years. I can't find a reference for that online now though; so obviously look it up if it interests you. Maybe some astrophysicist type can confirm or deny this?

    • Can anyone explain if the curent theories still speculate that eventually all the matter in the universe will be sucked up by black holes?

      If the universe is expanding or constant, then no. If the universe is expanding the distances involved would prevent this from happening. If the universe is constant, then again not likely due to the distances invovled. That I remember at the moment, I've not heard of any credible theories that would say that a given volume of space with a given amount of matter would cre


    • > Can anyone explain if the curent theories still speculate that eventually all the matter in the universe will be sucked up by black holes? Also, once that happens will the black holes (as the only remaining objects in spacetime) start attracting each other?

      Here [ucr.edu] is the most interesting thing I've ever read about the fate of the universe.

  • I'm lost (Score:5, Funny)

    by soundsop ( 228890 ) on Sunday August 07, 2005 @01:57AM (#13262570) Homepage

    Beware, the article is quite technical:

    If you extrapolate our 21 quasars out to the rest of the sky, you get a whole lot of quasars.

  • to the visible ones?

  • Smoke me a kipper! (Score:5, Funny)

    by NanoGator ( 522640 ) on Sunday August 07, 2005 @03:12AM (#13262773) Homepage Journal
    When asked why it took this long to discover the nature of the strange space phenomenon, Mark Lacy of the Spitzer Science Center at the California Institute of Technology replied:

    "Well, the thing about a Black Hole, its main distinguishing feature, is it's black. And the thing about space, your basic space color, is black. So how are you supposed to see them?"
  • Is this actually one of the few moments in Slashdot news when "Nothing to see here, please move along" is literally true?

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