[neilep (OP)]

Dearest Parsecologists,


Happy New Year !


Black Holes are just great. Occasionally they like to hang out and merge...which is nice.


Here is a true bona fide non doctored image that i just took:



  A true bona fide non doctored image of two back hole chums just moments ago.


Is it me or do I detect a touch of Pareidolia ? Nah, just me i guess !!

So in my understanding merging black holes is all well and good until they reach a distance from one another of one parsec. Then, something strange happens as they are not sheeposed to have enough of something to continue to merge !

• When galaxies collide, their central supermassive black holes (SMBHs) should also eventually merge.
• However, as the SMBHs approach each other within about a parsec (3.26 light-years), the density of stars and gas in the galactic core becomes too low to effectively remove the energy and momentum needed for the final plunge and merger.
• This "energy loss problem" prevents the black holes from spiraling inward and merging within a reasonable timeframe.
  
  So how do Black Holes merge then ?

If you can provide me with the solution I can then take the credit which will make me happy.

Thank ewe very much.

hugs and shmishes

mwah mwah mwah

Neil🐏🐏🐏🐏
Executive Officer Ruminant In Charge Of Asking This Question

[Halc]

    When galaxies collide, their central supermassive black holes (SMBHs) should also eventually merge.
    However, as the SMBHs approach each other within about a parsec (3.26 light-years), the density of stars and gas in the galactic core becomes too low to effectively remove the energy and momentum needed for the final plunge and merger.
    This "energy loss problem" prevents the black holes from spiraling inward and merging within a reasonable timeframe.

So how do Black Holes merge then ?

The quote you give kind of says it.  To get closer, their kinetic energy must go somewhere, else, like Earth, it just keeps orbiting the sun without getting closer.

Thing is, the way this energy is dissipated is by flinging other matter away, giving that matter the orbital energy of the pair. Once the material is all gone, only new (not orbiting) material can contribute further to this process, and that takes a lot of time.

They will eventually merge, just all all planets will eventually fall into the sun given enough time and no external dissturbance.  Any pair of orbiting objects emits gravitational waves and that energy comes from kinetic energy.. Earth for instance emits GWs at the rate of about 200 watts, and the kinetic energy of Earth will run a pair of 100W light bulbs for an awfully long time.  The sun will swallow Earth before that has time to happen, but that's the fate of say Jupiter.

Likewise, all black hole binaries like the undoctored picture you took will eventually merge, but the universe is only 14 billion years old, nowhere near long enough for gravitational waves to do the job at a full parsec away.


Fun fact: Two sheep circling each other will emit Baaavitational waves.

[evan_au]

Unfortunately, the length of current gravitational wave detectors does not allow us to detect the very low frequencies/long wavelengths of merging supermassive black holes. So we can't directly measure the rate of such events*.

There is an indirect indication that such mergers might occur, in the form of "X-shaped" radio galaxies; one theory suggests that a supermassive black hole was emitting a jet of matter from the poles of the accretion disk - and then it suddenly gets hit by another massive impactor, which changes the axis of rotation, and the direction of the polar jet.

In the images I have seen of these objects, there does not seem to be a large gap in the polar jets, suggesting no final parsec pause.
https://en.wikipedia.org/wiki/X-shaped_radio_galaxy

PS: This next paper suggests that the X-shaped radio galaxies might occur due to interactions between the jet and the accretion disk, which does not turn off the jet:
https://www.space.com/black-hole-feeding-x-shaped-galaxies

*Perhaps the proposed LISA space-based gravitational wave observatory will give a better idea of how common these are
https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna