Supercomputers supermodel supermassive black holes

Supercomputers supermodel supermassive black holes: "

What happens when two black holes smash into each another? They form an
even larger black hole while driving jets of relativistic matter into
the far reaches of the cosmos. New complex computer
simulations have attempted to give a glimpse into
the explosion of electromagnetic and gravitational waves that result.
The answers may tell us whether or not we could
ever detect such a merger.

A paper describing the simulations appears in the current issue of Science. It takes a look at what happens as two supermassive black holes dance
around each another, accompanied by a conducting plasma and magnetic field. The emission of gravitational waves would
carry both angular momentum and energy away, causing them to eventually collide and merge. The numerical simulations
indicated that the particle
jets that sometimes accompany black holes would align, thanks to an
anchoring and alignment of the magnetic field that occurs as they merge.

An interesting side note mentioned by the authors is that
stray charged particles will get caught up in the magnetic field and
accelerate to enormous velocities. This acceleration will result in
the particle radiating off enough energy to form electron-positron
pairs from the vacuum which will be accelerated in turn. This process
would repeat, producing a cascade of particles that populate the
immediate region with a charged, conducting plasma.

All of the work is interesting to any theorist, but the results show
what astronomers might look for as indications that an event of this sort has taken
place. The electromagnetic energy of the collision can be transferred to kinetic
energy through the plasma, which will bleed it off through synchrotron
radiation. Those emissions could be detected with future X-ray telescopes out to a significant distance from the source (a redshift of z
= 1).

Further in the future, joint
X-ray-gravitational wave detectors will allow more refined observations
of supermassive black hole mergers. The paper gives a scaling for
gravitational wave power that should be detectable at even greater distances, back to redshifts of 5 to 10.

Science, 2010. DOI: 10.1126/science.1191766

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