Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Trio of Big Black Holes Found in Galaxy Smashup

  1. Jun 25, 2014 #1
    by Dr. Ken Croswell

    Astronomers staring across the universe have spotted a startling scene: three supermassive black holes orbiting close to one another, two of them just a few hundred light-years apart. The trio, housed in a pair of colliding galaxies, may help scientists hunting for ripples in spacetime known as gravitational waves.

    Link: ScienceNOW.
     
  2. jcsd
  3. Jun 26, 2014 #2

    Drakkith

    User Avatar

    Staff: Mentor

    Nice. Hopefully we can find some more closer to home.
     
  4. Jun 26, 2014 #3

    SteamKing

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    That's OK. I like to keep my black holes as far away as possible. Too many things can go wrong if they're nearby.

    On the whole, I found the article in ScienceNow very confusing. First, the article mentions a couple of black holes orbiting one another although they are some 24,000 light years apart. Then, another pair of BHs is mentioned which are orbiting each other and are 450 LY apart. A third, previously described orbiting duo of BHs are some 24 LY apart. If these puppies attract each other strongly enough to orbit one another while separated by 24 LY, let alone 24 kLY, I want to be across the galaxy from them, or in another galaxy entirely.

    Who knows? Maybe it's already too late, and the solar system is already orbiting a BH somewhere.
     
  5. Jun 26, 2014 #4

    Drakkith

    User Avatar

    Staff: Mentor

    I think the article means that at first we thought it was just two black holes, 24 kly apart. Then, upon closer inspection, one of them was discovered to be a pair of black holes 450 ly apart. These two black holes are the 2nd tightest orbiting black holes, behind a pair that are 24 ly apart.
     
  6. Jun 26, 2014 #5

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Right.

    The trio is 4.3 billion light-years away, so it's completely safe for us :).

    It is hard to construct a scenario where this would happen without getting noticed. We orbit the center of our galaxy, where a massive black hole is a (small) part of the total mass, but I would not call that "orbiting the black hole".
     
  7. Jun 27, 2014 #6
    Do we have enough data to calculate when these will "collide" ? The mental image of a Black Hole Death Dance of an ever-tightening, ever-quickening spiral is just stupendous in every sense of the word and then some. Assuming we have data, is the Math equivalent to 2 bits of flotsam in a whirlpool, or is that altered by the fact that the force comes from "the flotsam" and not draining water?
     
  8. Jun 27, 2014 #7

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    For two orbiting black holes (or other isolated structures) in a completely empty space, it is easy to calculate the time they need to merge.

    Assuming the 450 light years distance and 4 million years for an orbit are right and assuming the orbit is roughly circular with two objects of equal mass, the black holes have masses of 3 billion solar masses (calculation.

    Plugging this into the formula for gravitational waves, we get a power of 5*1023 W. That is a lot compared to powers we use here on earth, but tiny compared to their kinetic energy of 1050 J. If you divide both numbers, you get a rough estimate of the mergin time: about 1 billion times the current age of the universe. Those black holes will continue to orbit each other long after all stars in the universe died, unless some other very massive object disturbs their orbit before.
     
  9. Jun 27, 2014 #8
    As much as a human mind can begin to comprehend such vast distances, I'm aware of the meaninglessness of my question as regards the 450 LY pair. I am more interested in the 24 LY pair and especially if there is some momentum vector from what I took to be "colliding" galaxies source, perhaps creating more of a spiral than a circling, stable orbit.
     
  10. Jun 27, 2014 #9

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Neglecting gravitational waves and other objects, the orbits are always ellipses (for bound systems). There are no spirals.

    Even for the 24ly-pair the timescale for gravitational waves is extremely long. Also keep in mind that the 24 light years are the minimal distance (the apparent distance as we just see two dimensions in the sky).
     
  11. Jul 2, 2014 #10
    This discovery was just featured on the John Batchelor Show. You can listen to the program at http://www.johnbatchelorshow.com/podcasts/2014/07/01/third-hour [Broken].
     
    Last edited by a moderator: May 6, 2017
  12. Jul 3, 2014 #11

    Borek

    User Avatar

    Staff: Mentor

    I wonder how rough it is, taking into account power is changing as r-5, so the process will speed up very quickly.

    Definitely no chance for me to witness the merge, just curious.
     
  13. Jul 3, 2014 #12

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Better than a factor of 10 - derivatives and integrals of r5 give factors of 5-6. As we are 9 orders of magnitude above the current age of the universe, that should be sufficient. We don't even know if the orbit is circular - if it is highly elliptical, I would expect a different result.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Trio of Big Black Holes Found in Galaxy Smashup
Loading...