Last year’s gravitational wave discovery
may have felt like the end of an era, a momentous
occasion in which a precise experiment finally
ended a hundred-year search to confirm a baffling
prediction made by Albert Einstein.
The discovery, instead, spawned an entirely
new field of astronomy, and the results are
finally starting to trickle in.
A team of researchers picked apart the data
from the three gravitational wave detections
that the Laser Interferometer Gravitational
Wave Observatories or LIGO have made since
being flipped on.
The scientists are far from making any conclusions,
and have a few options as to how black hole
pairs form.
Regardless of where this research takes them,
the final result will prove that distant black
holes, the ones that produced the gravitational
waves LIGO detected, aren’t like the ones
we know about.
Pairs of black holes spin like basketballs,
and how their spins align can determine how
they formed.
If the spins line up with the black holes’
orbit around one another, then the pair probably
formed together as the orbiting stars both
collapsed.
If the spins were in the opposite direction
from the orbits or misaligned, then one of
the black holes could have formed and another
one passed by and got trapped in an orbit
by the gravity, and could have even formed
in some strange black hole nursery, something
scientists certainly haven’t observed in
the Milky Way.
There’s even a chance the black holes formed
during the Big Bang.
Those black hole pairs would also have misaligned
spins but would spin much more slowly than
the black holes in the Milky Way.
Understanding black hole binary formation
now hinges on a numerical property of the
gravitational wave, known as the “effective
spin,” which might take on any value between
negative one and one.
Aligned spins always have an “effective
spin” value greater than or equal to zero.
This time around, the researchers have produced
several models and tried to fit them to the
effective spin values taken from all the previous
gravitational wave events.
The model presents evidence that if the individual
black hole’s gravitational wave-producing
pairs spin like the ones in our own galaxy
do, then the distant pairs are misaligned.
