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According to a new study, the collisions observed between two black holes, larger than 100 suns, each is the largest merger of this type ever recorded.
A team of astronomers discovered an event called GW231123, the Gravitational Wave Observatory (LIGO) of laser interferometers. Physicists call such ripples gravitational waves.
Gravity waves were predicted by Albert Einstein in 1915 as part of his theory of relativity, but he thought that they were too weak to be discovered by human technology. However, in 2016, Ligo detected them only when the black holes collided, proving that Einstein was correct (again). The following year, three scientists received an award for their important contribution to the development of what is called the “black hole telescope.”
Since the first detection of gravitational waves, Rigo and its sister instruments (Virgo in Italy and Kagura in Japan) have picked up about 300 signs of a black hole merger. “These incredible detectors are the most sensitive instruments humans have ever built,” said Mark Hannam, director of the Gravity Exploration Institute at Cardiff University in the UK and a member of the Ligo Scientific Collaboration. “So we are observing the most violent and extreme events in the universe.
However, GW231123 is not just because it is the exception among these 300 black hole mergers and is the largest of the collisions.
“We’re also a member of the Ligo Scientific Collaboration,” said Charlie Hoy, a researcher at the University of Plymouth in the UK. “As if this wasn’t enough,” he continued. “Black holes are likely to rotate as fast as physically possible. GW231123 presents a real challenge to understanding the formation of black holes.”
Gravitational waves are the only way scientists can observe collisions in binary systems where two black holes orbit each other. “Before we were able to observe them with gravitational waves, there was even a question of whether or not there were binaries of black holes,” Hannam said. “Black holes do not emit light or other electromagnetic radiation, so they cannot be viewed by any type of regular telescope.”
According to Einstein’s general theory of relativity, gravity is the extension of space and time, forcing an object to move through curved space. When an object moves very quickly to rotate a black hole, the curved space forms ripples that spread outward like waves.
According to Hannam, these gravitational waves are “risky weak” and there are limits to the information they can provide. For example, there is uncertainty about the distance of GW231123 from Earth. It could be up to 12 billion light years away. Hannam is confident about the mass of two black holes, which are thought to be about 100 times and 140 times the mass of the sun.
But these numbers are confusing. “There is a standard mechanism by which a black hole forms when a star runs out of fuel and dies and collapses,” Hannam said. “But there are masses who think it’s impossible for a black hole to be formed like that, and a black hole from the live van at GW231123, in the middle of that (mass) gap.
“Mass gap” Hannham refers to starting at a solar mass of about 60 and going up to about 130, but as it is in the theoretical range, there is uncertainty as to where this gap begins and ends. But if the black holes from GW231123 actually fell into this gap, they probably wouldn’t have formed. It collapses from the stars, but in other ways.
A study published Monday in the Open Access Repository Arxiv suggests that the “mass gap” could explain whether the two black holes were the result of previous mergers rather than the product of the dying star. “This is a mechanism people have spoken about in the past and I’ve seen some previous hints,” he said.
In this scenario, a chain reaction of black hole mergers occurs. “We can create this process that only accumulates larger and larger black holes. The black holes in GW231123 look like they can be seen by the masses who cannot obtain them by their usual mechanisms.
If this hypothesis is confirmed, it suggests that it is somewhere between the black holes formed from the death of a large star and the super-large black holes at the center of the galaxy, states the ultra-high Massive black holes found in the center of the galaxy. Wilkins was not involved in the discovery of GW231123.
“Gravity waves open a very interesting window into the black hole, revealing a truly interesting mystery,” he added. “Before the emergence of gravitational wave astronomy, only actively grown black holes could be detected by drawing in material and generating a powerful light source. Gravitational waves show different parts of the black hole population that are growing by fusing with other black holes rather than pulling the material.”
Another amazing feature of the GW231123 is how quickly the two black holes rotate with each other.
“So far, most of the black holes we’ve found in gravitational waves are spinning quite slowly,” said Charlie Hoy. “This may suggest that GW231123 may have been formed by a different mechanism compared to other observed mergers, or that the model needs to be changed.”
While such fast spins are difficult to produce, Hannam also supports the idea that black holes have undergone previous mergers, as scientists expect them to fuse faster.
“The GW231123 stands out as an extraordinary event that is inexplicable to challenge and interpret models of gravitational wave signals because of the complexity of modeling such (fast) spins.” “What surprised me most is what I still need to learn about gravitational waves. I really hope that in the future we can observe other events similar to GW231123 and improve our understanding of such systems.”
The previous record of the largest black hole mergers observed so far belongs to a merger called GW190521, which was 60% of the size of GW231123. However, scientists have said that even larger mergers could be found in the future, and that the collision may be observed one day through more accurate means that could be in the coming decades, such as the proposed space explorer in the US and the European Einstein telescope.
This new discovery opens a new window on how black holes form and grow, and Imre Bartos, an associate professor at the University of Florida, was not involved in the study. “It also shows how quickly gravitational wave astronomy matures,” he added. “In less than a decade, we moved from the first detection to the realm of charts, challenging our best theories.”
He agrees that previous mergers can explain both the high mass and fast spins of black holes, but other possibilities include repeated collisions of young star clusters and the direct collapse of unusually huge stars. However, he added that these possibilities are unlikely to produce black holes that spin this fast.
It is very natural to describe the black hole of GW231123 as the remains of one or more generations of previous mergers, said Zoltanheiman, a professor at the Austrian Institute of Science and Technology, who was not involved in the discovery. “The idea was already raised shortly after the initial Ligo detection of (black hole) mergers, but this new merger is extremely difficult to explain in other ways.”
Future detections say, “Was this heavyweight match the tip of the iceberg?”, he added.
