16 votes

Pair of supermassive black holes discovered on a collision course

10 comments

  1. [2]
    ammut
    Link
    The sheer magnitude of what is happening is nearly impossible for my brain to comprehend.

    Astronomers have spotted a distant pair of titanic black holes headed for a collision.

    Each black hole's mass is more than 800 million times that of our sun.

    The sheer magnitude of what is happening is nearly impossible for my brain to comprehend.

    8 votes
    1. mat
      Link Parent
      Nearly impossible? My brain can barely comprehend how far it is down the road to the chemist, let alone anything space related.

      Nearly impossible?

      My brain can barely comprehend how far it is down the road to the chemist, let alone anything space related.

      12 votes
  2. [8]
    Douglas
    Link
    So, to confirm my takeaway from the article, we don't know what's going to happen when these collide, but they've probably already collided, and are likely emanating gravitational waves that are...

    So, to confirm my takeaway from the article, we don't know what's going to happen when these collide, but they've probably already collided, and are likely emanating gravitational waves that are just now starting to reach us?

    Sorry if my skimming of it was way off, a bit of it went over my head.

    4 votes
    1. [7]
      Diff
      Link Parent
      If I'm reading this right, the waves aren't just now reaching us, they're not due here for another 2.5 billion years. The black holes are 2.5 billion light years away, and coincidentally from...

      If I'm reading this right, the waves aren't just now reaching us, they're not due here for another 2.5 billion years. The black holes are 2.5 billion light years away, and coincidentally from their current position it'll be another 2.5 billion years before any waves will arrive. So I think they've "just" started emitting the waves wherever they are now.

      5 votes
      1. [6]
        Anwyl
        Link Parent
        Gravity waves propagate at the speed of light. So if we can see the collision, we'll feel the gravity waves. In some sense the events happened 2.5 billion years ago.

        Gravity waves propagate at the speed of light. So if we can see the collision, we'll feel the gravity waves. In some sense the events happened 2.5 billion years ago.

        1. [3]
          Algernon_Asimov
          Link Parent
          Remember that the image we're seeing is pre-collision. We're seeing two black holes approaching each other: "Observed as they were 2.5 billion years ago, the newfound supermassive black holes...

          Remember that the image we're seeing is pre-collision. We're seeing two black holes approaching each other: "Observed as they were 2.5 billion years ago, the newfound supermassive black holes appear about 430 parsecs apart." And, then: "The two supermassive black holes are especially interesting because they are around 2.5 billion light-years away from Earth. [...] Coincidentally, that's roughly the same amount of time the astronomers estimate the black holes will take to begin producing powerful gravitational waves." In other words, they're not going to start producing gravitational waves until about now: "In the present-day universe, the black holes are already emitting these gravitational waves, but even at light speed the waves won't reach us for billions of years."

          @Diff is right: we're not going to detect these gravitational waves here for a long time.

          FYI: @Douglas.

          4 votes
          1. Archimedes
            Link Parent
            We might be able to detect other black hole collisions in this lifetime though.

            We might be able to detect other black hole collisions in this lifetime though.

            Based on the findings, Pardo and Mingarelli predict that in an optimistic scenario there are about 112 nearby supermassive black holes emitting gravitational waves. The first detection of the gravitational wave background from supermassive black holes should therefore come within the next five years or so. If such a detection isn't made, that would be evidence that the final parsec problem may be insurmountable.

            2 votes
        2. [2]
          Loire
          Link Parent
          It did happen 2.5 billion years ago + however long it took the two to traverse 400 parsecs + whether or not there is some slow down occuring within the final parsec.

          It did happen 2.5 billion years ago + however long it took the two to traverse 400 parsecs + whether or not there is some slow down occuring within the final parsec.

          1. Anwyl
            Link Parent
            The reason I'm using "in some sense" is because a) You can parametrize time however you want. b) We're seeing it now, so in some other sense "it's happening now". I'm guessing that sense is what's...

            The reason I'm using "in some sense" is because
            a) You can parametrize time however you want.
            b) We're seeing it now, so in some other sense "it's happening now". I'm guessing that sense is what's causing the misconception that the gravity wave will take 2.5 billion years to arrive.