The Theory of Relativity, published in 1905 by
Albert Einstein, postulated the existence of gravitational waves—oscillations
of the space-time fabric—and more than a century later, we have irrefutable
evidence of it. Now, a new study has managed to find clear indications of
relativistic precession in the orbits of two colliding black holes.
The science and other stuff to know
Since gravitational waves were first detected in
2015, this has become a fertile field for modern astrophysics, allowing experts
to spot phenomena they were previously blind to.
The merger of black holes is undoubtedly one of the
most colossal and violent events that can be conceived. The apocalyptic dance
that the two bodies perform as they approach their inexorable destiny, and the
fusion itself, involves so much energy that the fabric of space-time is shaken
as if it were a sheet.
Thanks to detectors called interferometers, we can
track these events from Earth and find out what event gave rise to these waves
and what region of the universe they come from. The GW200129 signal was
detected in 2020 and comes from the deadly gravitational dance of two massive
black holes.
Now, a team of researchers from Cardiff University
observed a strange twisting motion in the orbits of two colliding black holes,
a phenomenon predicted by Einstein, a press release states.
Their study, which has been published in Nature,
deduced that, before merging, these black holes rotated, presenting what is
known as relativistic precession: the tendency of an orbit to be perturbed and
change cyclically. A top, for example, is a clear example: it begins to rotate
on its vertical axis —not rotational— and eventually, the axis twists and
begins to rotate. This happens with the orbits of all systems where the gravity
of one body affects the other, and tends to be a negligible effect.
But the case of GW200129 is exceptional due to the
speed of precession of the system; it is 10 billion times stronger than the
fastest precession measured up to its detection—75 years.
So what?
In addition to continuing to provide evidence in favor of Relativity—one of the most complete physical theories and with the greatest predictive power—, this detection speaks of the ability that the gravitational wave field has developed to detect phenomena that are increasingly weaker at energy levels.
The refinement of data analysis techniques and the
collaborations between the LIGO, Virgo, and KAGRA interferometers are making it
possible to obtain more precise measurements.
What’s next?
The network of interferometers extended between the
United States (LIGO), Europe (Virgo), and KASGRA (Japan) is currently out of
service as they are carrying out maintenance on the delicate design of the
experiment. They will retake data in 2023 and track new events of this type
and, hopefully, many other unknown ones.
“So far most black holes we’ve found with
gravitational waves have been spinning fairly slowly,” said co-author Charlie
Hoy, in a press release. “The larger black hole in this binary, which was about
40 times more massive than the Sun, was spinning almost as fast as physically
possible. Our current models of how binaries form suggest this one was
extremely rare, maybe a one in a thousand event. Or it could be a sign that our
models need to change.”
The researchers hope to continue detecting phenomena
of this type. After all, the first detection of something always gives us the
wrong impression that what we have found is unique. Still, it is enough to
refine our measurements and instruments to realize that it is just one more
specimen among hundreds of thousands of others.
Reference: Nature