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Astronomers Discover Pair of Black Holes In Inactive Galaxy

Posted by Unknown on from the ate-all-the-other-stars dept.

William Robinson (875390) writes "The Astronomers at XMM-Newton have detected a pair of supermassive black holes at the center of an inactive galaxy. Most massive galaxies in the Universe are thought to harbor at least one supermassive black hole at their center. And a pair of black holes is indication of strong possibility that the galaxies have merged. Finding black holes in quiescent galaxies is difficult because there are no gas clouds feeding the black holes, so the cores of these galaxies are truly dark. It can be only detected by this 'tidal disruption event'."

27 of 45 comments (clear)

  1. Re:Science article!?!?! by 50000BTU_barbecue · · Score: 2
    Why? It means reptile.

    http://en.wikipedia.org/wiki/H...

    --
    Mostly random stuff.
  2. Re:Science article!?!?! by kruach+aum · · Score: 1

    No it doesn't. Herpetology is the study of amphibians and reptiles (which make about as much sense to study together as mammals and reptiles but whatever). "Herpeto-" comes from the greek herpeto, meaning "a creeping thing."

  3. Any chance of finding gravitational waves? by jfengel · · Score: 3, Interesting

    The discovery of pulsars rotating around each other by Hulse and Taylor was a major confirmation of general relativity because of the way they were radiating energy in gravitational waves. Is there any way to use black holes to confirm this even more? Would it be something we could help "point" a gravitational wave detector at?

    (Sorry, IANAP, so I apologize if this is a stupid question.)

    1. Re:Any chance of finding gravitational waves? by Anonymous Coward · · Score: 2, Informative

      Unfortunately the black holes are separated by a distance about a billion times their size, which makes energy loss by gravitational waves rather small, and would be difficult to see a change in their orbital period. Also, their separation is by a couple thousand light years, so it would take a long observation to see much change in their orbital position, and the frequency of the emitted gravitational waves would be very, very, very low. If there were a test here, it would probably be very subtle. The prime candidates would be things close together, orbiting on the time scale of seconds or less right before a collision.

    2. Re:Any chance of finding gravitational waves? by rotorbudd · · Score: 3, Informative

      . Also, their separation is by a couple thousand light years,

      TFA reads:
      "The separation between the black holes is quite small: 0.6 milliparsecs, or about 2 thousandths of a light year. That's about the width of our Solar System."
      So gravitation waves might be seen AT that distance

      --
      A bullet may have your name on it, but artillery is addressed to " Whom It May concern"
    3. Re:Any chance of finding gravitational waves? by towermac · · Score: 1

      doesn't gravity and light travel at the same speed?...

      If they discover the graviton, the answer to that will likely be yes. But atm, it is unknown.

      I don't see how it can be so though, according to my armchair physicist understanding of relativity. Gravity is the 'shape' of space-time. In other words, it's made out of the same thing as height, width, depth, and time. If that is the case, then gravity doesn't have to 'travel' anywhere; it was already there.

      That would mean gravity is instant. However, it seems to be an academic thought exercise, since gravity is the deformation of space-time by mass, you will never catch it going faster than light. The waves they refer to aren't gravity propagating outwards; but variations in the gravity, and thus space-time itself.

    4. Re:Any chance of finding gravitational waves? by Anonymous Coward · · Score: 1

      Good catch, as I had misread another source when I made that post, and thought it said 2 thousand light years. Still two thousandths light years means their orbital period is on the order of a year. That would still be a way too slow for gravitational detectors as we have now and in the near future (especially for any on Earth that might filter out things around that period).

      Observing a change in the orbit might be possible on human timescales at least, but would depend on how accurately they can locate their relative position and notice any changes. From the numbers given (0.002 ly seperation, ~1e6 M_sun masses), that would suggest the pair is radiating ~10^33 W of gravitational waves, but the total energy of the system is ~10^49 J, and it would take ~40 million years to collide taking into account the increasing power being emitted as they get closer. We would be looking for a ~0.5 parts per trillion (10s of microseconds) change in the orbital period over the time of a year. That would take a substantial improvement in observation abilities.

    5. Re:Any chance of finding gravitational waves? by Anonymous Coward · · Score: 1

      Yes, light and gravity is thought to travel at the same speed, with some measurements agreeing. The issue with why observing now would be bad is that the black holes are too far apart (even correcting couple thousand light years to couple thousandths). This means that the power emitted is lower than what it will be as they get closer, going roughly as inverse fifth power, so when they are half the current distance apart they will be emitting 32 times as much power in gravitational waves.

      It also means the period of the gravitational waves will be very long, and detectors have limited frequencies which they work over. Laser interferometers on Earth like LIGO look over maybe the 1 Hz to few kHz range, while space based ones are expected to get down to about 10^-5 Hz (waves with a period of about a day). Detection by looking at variation in timing of pulsars might give the ability to detect gravitational waves with periods on the order of 1-100 years, but would require really strong waves.(my rough estimate is this binary pair might be at least ~5 orders of magnitude too weak, although I'm less sure about some of these numbers).

    6. Re:Any chance of finding gravitational waves? by mythosaz · · Score: 1

      ...at least.

      The Sun's Hill Sphere is probably thousands of times farther out -- the point at which "everything else in the universe" can win out over slowly but surely being drawn into our solar system.

    7. Re:Any chance of finding gravitational waves? by Anonymous Coward · · Score: 1

      General Relativity has a *local* Poincare symmetry, which is invariance of physical properties under translations (moving backwards and forwards in space and/or time), rotations in space, and Lorentz boosts. There is one free parameter in a locally Poincare-symmetric spacetime, and that is the speed of a massless object, which is denoted "c". Light is expected to be massless (and this holds up well in the limit of our ability to measure), whether it's particles, or waves, or something like each, or something very different. Gravity is also expected to be massless, whether it's particles, or waves, or something like each, or something very different.

      Our universe is well-modelled by relativistic fields filling all space and time -- and gravity can be modelled that way as well. All the main fields we have discovered so far (except gravity) also quantize. Light's field quantum is the photon, for example. So people tend to expect that gravity quantizes too. Indeed, if gravity does quantize in our universe there is likely to be a -- perhaps not straightforward or easy -- formal mathematical correspondence between general relativity and quantum gravity, although that has not yet been discovered. (There are gauge/gravity formalisms that work exactly in (hypothetical) universes that are not much like ours and that has narrowed the differences between seeing gravitation as spacetime curvature and seeing gravitation as a relativistic quantum field theory by developing improved fits between the latter approach and what we see in nature). We already have a *classical* (as in not quantum as in parameters take real-numbered values and are not constrained in terms of possible values) field theory of gravitation and that's General Relativity (GR).

      One of the neat things about GR is that it is founded on equivalencies, and the classical field / curved manifold equivalence is embedded right in the Einstein Field Equation simply by moving things between the right and left sides of the equations. Consequently, gravitation can be modelled as waves in a classical field (one needs to exercise some care in choosing appropriate coordinates and so forth) moving matter about in full agreement with the usual view of matter moving in response to spacetime curvature.

      Additionally, there is a generalization of the conservation of energy that exists in GR, called the conservation of energy-momentum. It follows from an analysis of GR's symmetry group and Noether's Theorem which says that wherever there is a symmetry there is a conservation law. The GR symmetry allows energy to flow between the gravitational field and the other fields, and we see many examples of this in the sky. One of them is that moving massive compact objects excite the gravitational field (but only slightly and the amplitude falls off rapidly), and since those excitations are waves they can interfere with one another constructively, making it possible to detect at great distances with current technology (in principle anyway), given two fast-moving (relative to one another *and* to us) highly massive very compact objects.

      These interference patterns are excitations in a field in which excitations are massless, so they are expected to move at 'c'.

    8. Re:Any chance of finding gravitational waves? by Anonymous Coward · · Score: 1

      One of them is that moving massive compact objects excite the gravitational field (but only slightly and the amplitude falls off rapidly), and since those excitations are waves they can interfere with one another constructively, making it possible to detect at great distances with current technology (in principle anyway), given two fast-moving (relative to one another *and* to us) highly massive very compact objects.

      Not sure what interference has to do with it in general or the ability to detect it over long distances. Although GW is a little different to someone used to EM waves, because it requires a change in quadrupole moment, it is still like a radiating EM field from a change in dipole moment and just a wave in the far field. As long as there is nothing that can absorb it significantly, and there are not too many sources, it could be measured as far away as you want given travel time and a detector with a low enough noise floor.

  4. Increasingly important topic by l2718 · · Score: 1

    As we understand galaxy formation better, galaxy mergers are an increasingly important topic. It's cool to have direct evidence of this type; probably this will spur more merger simulations designed to track the black holes.

    1. Re:Increasingly important topic by gstoddart · · Score: 4, Funny

      As we understand galaxy formation better, galaxy mergers are an increasingly important topic.

      Unfortunately, as always happens in such things, after the merger many stars will lose their jobs as the galaxies try to cut costs. They may also decide to outsource some of the jobs of the current stars to neighboring galaxies, and some existing customers might get screwed over as they decide to get rid of product lines the larger galaxy isn't interested in.

      Mostly these things benefit the big giant holes running things.

      --
      Lost at C:>. Found at C.
  5. Re:Science article!?!?! by 50000BTU_barbecue · · Score: 1

    In the link I provided it states ""Herp" is a vernacular term for reptiles and amphibians. It is derived from the old term "herpetile", with roots back to Linnaeus' classification of animals"

    If you feel this is in error, feel free to edit the wiki.

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    Mostly random stuff.
  6. Inactive? by Nidi62 · · Score: 1

    So how do they know it's inactive? Are all the lights out?

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    The only thing necessary for evil to triumph is for it to be pitted against a slightly greater evil
    1. Re:Inactive? by DudemanX · · Score: 3, Informative

      It's "inactive" in the sense that it isn't Active. The Milky Way is also inactive.

      I'm guessing that if these two black holes get close enough then that galaxy could get very active very quickly.

  7. Lost civilizations? by Grishnakh · · Score: 1

    I wonder if there were any civilizations in these galaxies which merged, which were sucked into the black holes.

    1. Re:Lost civilizations? by Intrepid+imaginaut · · Score: 1

      Chilling thought really, late developing civilisations struggling to develop an interstellar, even intergalactic presence, pitting their collective intelligences against the growing cold and dark and the slipknot of gravity. I wonder would we ever be able to excavate black holes to find their last transmissions.

    2. Re:Lost civilizations? by towermac · · Score: 1

      And even if their collective intelligence won out, it may still take them 10,000 years or so to actually fly out of it.

      From our perspective...

  8. Scientists at XMM? by xiox · · Score: 2

    "Scientists at XMM-Newton" - who writes this rubbish? XMM is a European space X-ray observatory in elliptical orbit around the earth. Nobody is "at" XMM.

  9. Re:How long til they collide? by durrr · · Score: 1

    Rothschild radius is the volume around a bank in which we no longer know what happens to the money or internal policies of the bank.

    It's larger than the Earth nowdays.

  10. Really? by g01d4 · · Score: 1

    Finding black holes in quiescent galaxies is difficult because there are no gas clouds feeding the black holes, so the cores of these galaxies are truly dark. It can be only detected by this 'tidal disruption event'."

    The dark cores have been observed in light curves http://arxiv.org/abs/1310.5310

  11. Re:How long til they collide? by HiThere · · Score: 1

    "Roche's limit" is what you are looking for, but I don't know that it applies to balck holes.

    --

    I think we've pushed this "anyone can grow up to be president" thing too far.
  12. Re:Science article!?!?! by JasonGoatcher · · Score: 1

    I prefer herpaderpology, the study of idiots.

  13. Re:Science article!?!?! by garyebickford · · Score: 1

    Closely related to ropadopology, pretending to be an idiot

    --
    It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
  14. Perhaps there are more black holes than we thought by dtjohnson · · Score: 1

    If a pair of black holes are present in a quiet galaxy, perhaps there are also black holes present where there aren't any galaxies at all...'between' galaxies. Maybe black holes were the driver for all galaxy and star formation and maybe there are more black holes than there are galaxies. Maybe way way more. Maybe such black holes are the missing dark matter that we are searching for.

  15. Re:How long til they collide? by HiThere · · Score: 1

    This is true, but the term he was looking for was Roche's limit. I suspect, however, that it doesn't apply to black holes. More precisely, I suspect that the Roche limit is within the Schwarzchild limit. This might, possibly, depend upon the speed with which the two holes revolve around each other...but I doubt it. Still, the math to solve that is way over my head.

    An additional factor, of course, would be the rotational speed of each black hole. Things get a lot more complicated than I can solve *very* quickly. But I *suspect* that the event horizon doesn't become very permeable. (Does the rate at which the black hole emits Hawking radiation depend on how fast it is rotating? On the presence of an external gravitational field? Yiii!)

    Probably the Roche limit is within the Schwartzhild limit, so none of this applies. If it does, then the black hole would probably need to disintegrate via Hawking radiation. OTOH, the problems of spinning black holes, and of charged and spinning black holes, even in isolation are so complex that I don't believe that anyone has yet solved them. (It's been decades since I looked at the question, so I may be wrong.) When you add in a rotating external gravitational field.... well, I don't trust simple assertions that work in most cases. This could well be an edge case that would yield a different result.

    --

    I think we've pushed this "anyone can grow up to be president" thing too far.