Shortly before they collided, two black holes were intertwined in spacetime to knots


in February 2016and scientists in Gravitational Wave Laser Interferometer LIGO announces the first-ever discovery of gravitational waves (GW). Originally predicted Einstein’s theory of general relativity, these waves are ripples in spacetime that occur when massive objects (such as black holes and neutron stars) merge. Since then, countless events have been discovered by observatories around the world – so much so that they have become an almost daily occurrence. This has allowed astronomers to gain insight into some of the most extreme objects in the universe.

in recent studyan international team of researchers led by Cardiff University observed a binary black hole system originally discovered in 2020 by advanced legoAnd the VirgoAnd the Kamioki Gravitational Wave Observatory (Kajra). In the process, the team observed strange spinning motion (also known as precession) in the orbits of colliding black holes that was 10 billion times faster than what was observed with other precursor objects. This is the first time a start has been observed with binary black holes, confirming another phenomenon predicted by general relativity (GR).

The team was led by Professor Mark Hannam, Dr. Charlie Hoy, and Dr. Jonathan Thompson from Gravity Exploration Institute at Cardiff University. Joined by researchers from LIGO . LaboratoryThe Barcelona Institute of Science and TechnologyThe Max Planck Institute for Gravitational PhysicsThe Institute of gravitational wave astronomyThe ARC Center of Excellence for the Detection of Gravitational WavesThe Scottish Universities Physics Alliance (SUPA), and other GW research institutes.

Binary black holes (BBHs) are a prime candidate for research in GWs because astronomers expect that some of them will be made up of predawn binaries. In this scenario, the black holes would orbit each other in constantly narrowing orbits, generating an increasingly strong GW signal until they merge. However, no conclusive evidence of orbital precession has been observed from the 84 BBH systems detected by Advanced LIGO and Virgo so far. However, the team noticed something different when examining the GW200129 event that it discovered LIGO – Virgo – KAGRA collaboration during its third operational run (O3).

One of the black holes in this system (about 40 solar masses) is considered the fastest black hole detected by gravitational waves. Contrary to all previous observations of BBHs, the rapid rotation of the system has such a profound effect on spacetime that the entire system oscillates back and forth. This type of proactiveness is known as frame drag (aka the Lense-Thirring effect), an interpretation of GR in which gravitational forces are so strong that they “pull” the very fabric of spacetime with them.

This same phenomenon is seen when observing the orbit of Mercury, which periodically advances as it orbits the Sun. In short, Mercury’s path around the Sun is very eccentric, and the farthest point in its orbit (perihelion) also moves over time, revolving around the Sun like a rotating top. These observations are one of the ways GR was tested (and confirmed) after Einstein formalized it in 1916. In general, precession in general relativity usually has such a weak effect that it is almost imperceptible. As explained by Dr. Thompson at Cardiff University recently press release:

“It’s a very difficult effect to identify. Gravitational waves are very weak and their detection requires the most sensitive measuring instrument in history. Anticipatory motion is a weaker effect buried within the already weak signal, so we had to perform careful analysis to detect it.”

Previously, the fastest known example was a binary pulsar that took more than 75 years for the orbit to process. In this case, the BBH known as GW200129 (observed January 29, 2020) is processing multiple times per second, an impact 10 billion times stronger than a binary pulsar. However, confirming that black holes in this system were a priori has been a major challenge. Dr Hoy, now a researcher at the University of Portsmouth, said:

“Until now, most black holes we’ve found with gravitational waves have been orbiting relatively slowly. The largest black hole in this binary, which was about 40 times the mass of the Sun, was spinning as fast as physically possible. Our current models of how the binaries are formed suggest that this The model was very rare, maybe one in a thousand. Or it could be a sign that our models need to change.”

These results confirm that before black holes merge — the most extreme gravitational event astronomers have ever observed — BBHs can experience orbital motion. It is also the latest in a long line of examples showing how GW astronomy allows astronomers to probe the laws of physics under the harshest conditions imaginable. With a network consisting of advanced LIGO, Virgo and KAGRA detectors in the United States, Europe and Japan, it is also one of the most vital areas of astronomical research.

This network is currently being upgraded to enhance its sensitivity to GW events and will begin its fourth round of observations (O4) in 2023. When that happens, it is hoped that several hundred black hole collisions will be discovered and added to the GW catalog. This will allow astronomers to gain more insight into the most extreme gravitational phenomenon in the universe and inform them whether GW200129 is an anomaly or whether such extreme events are common.

This research was funded by Science and Technology Facilities Council (STFC) – part of Research and innovation in the UK (UKRI) – The European Commission European Research Council (ERC). The paper describing their findings is titled “Proactive General Relativity in a Black Hole BinaryRecently appeared in the magazine temper nature.

In-depth reading: Cardiff UniversityAnd the temper nature


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