Apparently as part of the merger of galaxies, sometimes the central supermassive black holes of colliding galaxies get really close, however once they come to a distance of about <1 parsec, it seems that various forces conspire to keep the supermassive holes apart for the most part (see final parsec problem).

Is that true, and if so, what accounts for it? I assume it has something to do with orbital momentum, but I would have still expected the two to rather naturally merge...

  • $\begingroup$ To shed the required amount of angular momentum a lot of additional mass is needed that has to be threaded trough what is probably the eye of a needly in astronomical terms... just waving a giant black foam hand here... I am actually surprised that these things seem to happen at all. $\endgroup$ – CuriousOne Feb 8 '16 at 23:24
  • $\begingroup$ Serban, please give a source for this claim $\endgroup$ – Mitchell Porter Feb 8 '16 at 23:56
  • $\begingroup$ Yes I would like to see a source for this claim also thanks $\endgroup$ – Bill Alsept Feb 9 '16 at 0:29
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    $\begingroup$ It's hard to answer this directly, but the end answer will be "gravitational radiation is how the black holes fall in, and gravitational radiation is weak, because it couples with $G$ and the leading term is the quadrupole term" $\endgroup$ – Jerry Schirmer Feb 9 '16 at 0:32
  • $\begingroup$ How to think about the magnetic fields from both BH? $\endgroup$ – HolgerFiedler Feb 9 '16 at 6:08

I would have to see the source to answer completely but my first guess would be that the relativistic jets from the black holes are pushing against each other. This might cause some strange wobbling but I would think eventually the equators would lineup and they would begin to orbit each other.

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  • $\begingroup$ Couldn't relativistic jets be perpendicular to the plane of the colliding black holes, in many cases? In that case, there would be little to no effects from the jets. $\endgroup$ – HDE 226868 Feb 9 '16 at 1:49
  • $\begingroup$ Yes I would think so $\endgroup$ – Bill Alsept Feb 9 '16 at 2:40

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