Black Hole Binary En Route to Merger?

8 thoughts on “Black Hole Binary En Route to Merger?

  1. Jim-BaughmanJim-Baughman

    A problem presents itself with the merger of these two, or any two, black holes.

    According to the theory of relativity, the closer these holes approached each other the slower time in their vicinity would move from our perspective, so even if we found a pair calculated to merge within the next five years or so we would never see them merge. They would simply get closer and closer to each other; reducing their separation by half, then by half again, then again, ad infinitum.

    So the question arises–how is it that some GRBs have been postulated as coming from the merger of two back holes, since from our vantage this phenomenon cannot possibly ever be completed?

  2. Jim-BaughmanJim-Baughman

    A problem presents itself with the merger of these two, or any two, black holes.

    According to the theory of relativity, the closer these holes approached each other the slower time in their vicinity would move from our perspective, so even if we found a pair calculated to merge within the next five years or so we would never see them merge. They would simply get closer and closer to each other; reducing their separation by half, then by half again, then again, ad infinitum.

    So the question arises–how is it that some GRBs have been postulated as coming from the merger of two back holes, since from our vantage this phenomenon cannot possibly ever be completed?

    1. Peter WilsonPeter Wilson

      What happens is their separation keeps reducing until it equals the Schwarzchild radius of their combined mass. At that point, the event horizon has enveloped the pair, and no more information is available, except the total mass and angular momentum of the system. I.e, for all practical purposes, the two have merged.

      1. Jim-BaughmanJim-Baughman

        Thanks for the reply, but you are describing events from the point of view of the black holes. From our perspective (per relativity) it is impossible for the two event horizons to touch (let alone envelop the pair of black holes) because time is stopped dead at the event horizon of each hole. (That’s why the word “event” is in the term–no more “events” past that point because there is no time for them to unfold in.) Regardless of Schwarzchild radius or any other parameter, for anyone watching from earth the two event horizons can only approach each other ever more slowly but never meet, even after quadrillions of earth-years.

  3. Peter WilsonPeter Wilson

    Jim: The idea of BHs merging is correct; your idea of time “stopped dead” is incorrect.
    Your incorrect idea is probably based on the popular “simplification” of the situation, so grossly simplified it is wrong. Imagine dropping a clock into a BH, and watching it through a telescope from a safe distance. The popular accounting goes like this:
    As the clock nears the event horizon, you will see its second-hand slow down. Eventually, the clock will come to a complete stop, hovering just above the event horizon. It will hang there, frozen in time, never falling in, because at the event horizon…time stops!
    Reality: The clock will go into orbit around the BH. Tidal forces will rip it apart into subatomic particles, smearing it into a mini accretion disk. This will heat up, radiating first infrared, then visible light, then UV, x-rays and gamma rays. At that point, about 95% of the subatomic particles from our former clock will be shot out the BH’s twin jets, a la the iconic Cygnus A. Then the radiation will fade in reverse order: x-rays, UV, visible, IR, etc, to the point of invisibility.
    In other words, we will never see time “stop.” The last we will see of our clock is a fade-to-black as its subatomic remains race around the BH at nearly the speed of light.

  4. Jim-BaughmanJim-Baughman

    I just can’t get you to grasp what relativity is…don’t mean to be insulting, but time at an event horizon operates in different ways depending on one’s status as an observer. I’ll quote from Wikipedia, since the situation is laid out clearly and simply in short sentences, and happens to outline things correctly. Please note the highlighted parts:

    “An event horizon is most commonly associated with black holes. Light emitted from beyond the event horizon can never reach the outside observer. Likewise, any object approaching the horizon from the observer’s side appears to slow down and never quite pass through the horizon, with its image becoming more and more redshifted as time elapses.”

    Please let me repeat: [A]ny object approaching the horizon from the observer’s side appears to slow down and never quite pass through the horizon.

    This holds true whether it is a clock, a bobby pin, a kangaroo rat or another black hole that is approaching an event horizon. Whether you are prepared to grasp this or not, a conundrum exists. Surely you would not argue that a black hole merger could be prevented by people watching two approaching holes through a telescope, but that it would be completed as soon as they took their eyes off the encounter?

  5. Peter WilsonPeter Wilson

    Well Jim, you leave me no choice but to edit the Wikipedia page…

    Seriously, think about that quote. “…its image becoming more and more redshifted as time elapses.” Compare to mine: “Then the radiation will fade in reverse order: x-rays, UV, visible, IR, etc, to the point of invisibility.” Wiki and I agree on that much. It will not appear to slow down. It will appear to go faster and faster until it redshifts into blackness. And when the blackness of the object approaching the horizon becomes becomes indistinguishable from the blackness of the black hole…you could say the two have merged.

    On the other hand, you could argue that they really haven’t… 😉

    1. Jim-BaughmanJim-Baughman

      You are the kind of person whose life work seems to be muddling established science in favor of your own kooky misinformation. I will attempt to exert pressure to keep you from damaging Wikipedia entries on science in the future, since your tossing around of arcane (albeit irrelevant) terms in this discussion shows you obviously don’t know what you are talking about, and can only wreak havoc for the sake of seeming to win an argument you lost at the outset due to your ignorance of simple physics.

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