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Largest Black Hole Measured

Posted by kdawson on from the that's-no-moon dept.

porkpickle tips us to a BBC article on the quasar OJ287, a binary object containing largest black hole yet discovered, weighing in at 18 billion times the mass of Sol. Researchers were able to estimate its mass due to the presence of a smaller black hole in orbit around it. When the smaller companion's orbit intersects OJ287's accretion disk, once every 12 years, it triggers a burst of radiation that was detected by the Spitzer Space Telescope. More detail and a diagram are available on the Turku University site.

22 of 170 comments (clear)

  1. eh? I don't get it? by Anonymous Coward · · Score: 4, Interesting

    How large can a singularity be?

    I mean, if they used the word "massive" I'd get it. But large?

    1. Re:eh? I don't get it? by AmaDaden · · Score: 4, Informative
      It think they are not 100% sure about the whole "a black hole is a singularity" thing.

      quantum mechanics .... does not allow objects to have zero size--so quantum mechanics says the center of a black hole is not a singularity but just a very large mass compressed into the smallest possible volume.
      from http://en.wikipedia.org/wiki/Black_hole
    2. Re:eh? I don't get it? by pclminion · · Score: 4, Informative

      A black hole has an event horizon. This horizon has a very well-defined size.

    3. Re:eh? I don't get it? by moderatorrater · · Score: 4, Informative

      The event horizon is often considered the size of a black hole since nothing could ever leave that space.

    4. Re:eh? I don't get it? by BobGod8 · · Score: 5, Informative

      Actually it's way more complicated than that. Only non-rotating black holes could ever truly be point masses. Any angular momentum creates complicated tidal effects near the center, resulting in a non-point-mass. Carried further, the "singularity" expands until the point where it would effectively reach the event horizon itself, resulting in a naked singularity, which some calculations have shown can have actual size. Adding further rotation will (to a point), actually change the size of the "singularity". Of course, this is all moot, since that's not at all what the article was talking about, but that's my .02$.

    5. Re:eh? I don't get it? by Anonymous Coward · · Score: 5, Informative

      That's misleading, and I'm guessing you don't really understand what you're describing. A rotating black hole (aka every black hole, to some extent), is still a singularity (no need for quotation marks, it still has zero volume) despite not being a point. It's a ring with zero cross-sectional area, sort of like an infinitely thin thread arranged in a circle.

      Furthermore, this thread is based on quibbling over semantics without really understanding what the author quite validly meant. The "black hole" aspect of a singularity is a description of the effects of its event horizon, which of course scales with mass. A more massive black hole is by definition larger then a less massive black hole. Someone mod this up so this misunderstanding can be cleared up for more people.

  2. Wow. by AltGrendel · · Score: 4, Funny
    A binary black hole system.

    Proctologists across the globe swoon!

    --
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    - Douglas Adams

  3. Ask slashdot by sm62704 · · Score: 4, Funny
    Is there a theoretical limit to the size of a black hole?

    That was serious, here's the link to the non-serious.

    A Black hole is an impossible object which makes the Universe work. It has the useful property of being "undetectable". It's like when your spouse comes home with a dent in the car, and blames it on an invisible black mass; the dent is proof of the black mass, but you can't, and never will be able to see it with CCTV cameras, but you know it's there. "Dark matter" is an equally undetectable force that causes cars to defy gravity, and hit invisible black holes. Astronomers will tell you that lots of them have spouses with dents in their cars, and can explain this is very technical terms, so you won't be able to understand why it's not possible.
    More there...
    --
    mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
    1. Re:Ask slashdot by ArcherB · · Score: 4, Informative

      Is there a theoretical limit to the size of a black hole? While I can't give you numbers since I'm going from memory, but there used to be a theoretical limit to black hole size. This was before "Super Massive Black Holes" were discovered in the center of every galaxy. Super Massive Black Holes are much more massive than the previous theoretical limit and were thought to be impossible so many astronomers were claiming that such a thing was couldn't exist while others were saying, "Oh yeah? Then why don't you put down the chalk, professor, and come down to my observatory and tell me what that big-ass black gravity thing is in the middle of our galaxy!" (Of course, they couldn't really see it, but you get the point)

      I think astronomers are reluctant to guess at a size limit now as they don't want another discovery to make them look like asses.
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  4. Re:that's a lot by Anonymous Coward · · Score: 3, Informative

    My googling says its even more impressive (http://curious.astro.cornell.edu/question.php?number=31) 100 billion stars in the Milky Way and most are smaller than the sun, so 18 billion makes it very greedy indeed!

  5. Need a better measurement comparison by vjmurphy · · Score: 4, Funny

    "largest black hole yet discovered, weighing in at 18 billion times the mass of Sol."

    Yes, but how many Twinkies is that?

    --
    Vincent J. Murphy
    Spandex Justice
    1. Re:Need a better measurement comparison by wizardforce · · Score: 5, Funny

      Yes, but how many Twinkies is that?
      heh.. just for the heck of it: mass of twinkie: ~35 grams, mass of sun =2*10^30 kg, mass of blackhole: 18*10^9 sol therefore, 18*10^9*2*10^30/35g*1000g/kg~= 10^42 twinkies.
      --
      Sigs are too short to say anything truly profound so read the above post instead.
    2. Re:Need a better measurement comparison by networkBoy · · Score: 3, Funny

      You know, somehow that 42 is the exponent for number of twinkies in a black hole makes me worry about life, the universe, and everything....
      -nB

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      whois gawk date unzip strip find touch finger mount join nice man top fsck grep eject more yes exit umount sleep dump
  6. Question about gravity by caywen · · Score: 5, Interesting

    One question I have about gravity and black holes is this: If nothing can escape the event horizon, how can gravity escape it? In other words, would objects outside the event horizon ever feel the pull of gravity from that which is inside the event horizon?

    1. Re:Question about gravity by Anonymous Coward · · Score: 3, Interesting

      Gravitational pull isn't something that is being radiated out of bodies. Just changes of it.

      (In fact if the singularity somehow disappeared magically the outside world wouldn't detect it since the signal of black hole disappearing wouldn't escape from the gravitational well.)

    2. Re:Question about gravity by Ambitwistor · · Score: 3, Informative

      Other people have answered your question (radiation cannot escape from inside the horizon, but it can still generate a static external field), but here is a FAQ with more detail, including the quantum picture.

  7. That's incredible! by renfrow · · Score: 5, Informative

    Using this illustration and my trusty piece of paper straight edge, I estimate the long axis of the orbit to be 21000 AU and the minor axis to be 16000 AU. Using Ramunjan's Approximation for the circumference of the elliptical orbit and converting to light years, I guesstimate the circumference of the orbit to be ~1.99 (call it 2) light years.

    For a 12 year orbital period this means that the orbiting black hole is AVERAGING 1/6c (~49965km/sec, call it 50k km/sec)... meaning at periquaserion it's really booking! Much faster than The Dash!

    Tom.

  8. And so... by Cleon · · Score: 3, Funny

    I think this finally means that we have a definition for the SI unit "fuck-ton."

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    Gifts for Geeks - Stuff that really matters!
  9. Re:that's a lot by HAKdragon · · Score: 4, Funny

    Hawking: Homer, your theory of a donut shaped universe intrigues me

    --
    "Our opponent is an alien starship packed with atomic bombs. We have a protractor."
  10. Re:orbiting blackholes? by sentientbeing · · Score: 3, Interesting

    A holer system.

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    beware he who would deny you access to information, for in his mind he dreams himself your master
  11. Re:orbiting blackholes? by Ambitwistor · · Score: 4, Informative

    It is highly unlikely that a black hole would have planets orbiting it, as the planets would have insufficient mass to keep from simply falling in to the black hole, If the Sun collapsed into a black hole, its gravitational pull on the Earth wouldn't change.

    that is to say the overwhelming mass of the black hole would place the barycenter of the black hole and any accompanying planet well inside the event horizon, Maybe you're talking about supermassive black holes, but if you're talking about black holes in solar systems, formed from collapsed stars, that's not true. A black hole is not "overwhelmingly massive"; it generally has less mass than the star it formed from, since some mass may be lost during the collapse. (Unless it gains a lot more later ...)

    Furthermore, as the Earth-Sun barycenter is well outside the Sun's Schwarzschild radius, it would be outside the event horizon of a solar-mass black hole, too. Not that the location of the barycenter even matters to the stability of the orbit.

    There are exoplanets — the first discovered, actually — known to orbit neutron stars, which are only 10-20 km in radius. There's no reason why planets couldn't orbit black holes too.
  12. Re:no pictures by Arthur+Grumbine · · Score: 3, Insightful

    Neither of them are working for me today
    "Today"?! How often do you feel the need to stare at a gaping anus?!?
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    Now that I think about it, I'm pretty sure everything I just said is completely wrong.