Data from the Gemini North Telescope provide a possible explanation for the halting of the merger of a pair of supermassive black holes at the center of a galaxy
Almost every massive galaxy hosts a supermassive black hole at its center. When two galaxies merge, their black holes can form a binary pair, meaning they are in bound orbit. It is assumed that these pairs are prone to eventually merge, but this has never been observed. The question of whether such an event is possible has been a topic of debate among astronomers for decades. In a recent article published in The Astrophysical Journal, a team of astronomers presented new insights into this question.
The team was supported by data from the Gemini North Telescope in Hawaii, one of the two halves of the Gemini International Observatory (the southern one is in Chile) operated by NSF's NOIRLab, funded by the US National Science Foundation, to analyze a pair of holes Supermassive blacks located in the elliptical galaxy B2 0402+379. It is the only pair of supermassive black holes ever observed in sufficient detail to see the two objects separately, and it holds the record for the smallest distance directly measured – just 24 light years. Although this close distance heralds a powerful union, further study has revealed that the pair has been stuck at this distance for over three billion years, which begs the question; What is delaying the process?
To better understand the dynamics of this system and the merger halt, the team looked at archival data from the Gemini North Many Object Spectrograph (GMOS), which allowed them to determine the speed of stars in the vicinity of the black holes. "The excellent sensitivity of GMOS allowed us to map the increase in the velocities of the stars as you approach the center of the galaxy," said Roger Romney, professor of physics at Stanford University and co-author of the paper. "However, we were able to calculate the total mass of the black holes residing there."
The team estimated the pair's mass at 28 billion times the mass of the Sun, making the pair the heaviest pair of black holes ever measured. This measurement not only provides valuable context for the formation of the binary system and the history of the host galaxy, but also supports the long-held theory that the mass of a supermassive binary black hole plays a key role in delaying a potential merger.
"The data archive serving the International Observatory contains a goldmine of scientific discoveries that have yet to be explored," says Martin Steele, NSF program manager for the Gemini Observatory. "The mass measurements for the pair of extreme supermassive black holes are an impressive example of the potential impact of new research exploring this rich archive."
Understanding how this pair formed can help predict if and when they will merge—and some clues point to the pair forming through the merger of multiple galaxies. The first is that B2 0402+379 is a 'fossil cluster', meaning it is the result of an entire cluster of stars and gas merging into one giant galaxy. In addition, the presence of two supermassive black holes, along with the large combined valve, indicates that they were formed from the merger of several smaller black holes from several galaxies.
After galaxy mergers, supermassive black holes do not hit each other directly. Instead, they begin to bounce off each other as they settle into orbit around each other. Each time they get closer, energy is transferred from the black holes to the surrounding stars. As they lose energy, the pair are drawn closer and closer together until they are only a few light years apart, where gravitational waves begin and they merge. This process has been observed directly in pairs of stellar mass black holes – the first ever recorded case was in 2015 through the detection of gravitational waves – but never in a pair of the supermassive type.
With the new knowledge of the system's enormous mass, the team concluded that an exceptionally large number of stars were needed to slow the pair's orbit enough to bring them closer together. During the merger, the black holes appear to have ejected almost all of the material in their vicinity, leaving the galaxy's core depleted of stars and gas. Since there was no more material left to further slow the pair's trajectory, their union stalled in its final stages.
"Generally, galaxies with lighter black hole pairs seem to have enough stars and mass to drive the two together quickly," Romney said. "Because this pair is so heavy, it required a lot of stars and gas to do the job. But the pair cleared the central galaxy of such material, leaving it stranded and available for our study.”
Whether the pair will overcome their blasts and eventually merge over millions of years, or continue in orbital limbo forever, is yet to be determined. If they merge, the resulting gravitational waves will be a hundred million times more powerful than those created by stellar mass black hole mergers. It is possible that the pair could overcome the final distance through another galaxy merger, which would inject more material into the system, or perhaps a third black hole, which would slow the pair's orbit enough to merge. However, given B2 0402+379's status as a fossilized cluster, another galaxy merger seems unlikely.
"We look forward to further studies of the B2 0402+379 core where we will test how much gas is present," says Tirth Surti, a Stanford University graduate student and lead author on the paper. "This should give us further insight into whether the supermassive black holes can eventually merge or whether they will remain stuck as a binary pair."
More of the topic in Hayadan:
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Here is a response from ignorance. A black hole has long been photographed and filmed and is proof of the victory of science. But in Israel the anti-scientific forces will win in the end.
Hahahahaha every time I see these articles I burst out laughing. They take science fiction and try to present it as reality. And there are still people who buy this nonsense. These scientists and professors do not know what is here on Earth and are trying to reach distances of light years and explore there using telepathy, which is really a joke.