by “What came first, the galaxy or its monster black hole?”
Technically, it is an even more ancient riddle than the one about the chicken or the egg – although we have only recently become aware of it. And, according to new research, scientists may finally have an answer.
Supermassive black holes that existed near dawn have long been believed to have shaped the galaxies around them, accelerating the galaxies’ star formation rates and thereby influencing the evolution of the entire universe. But now, a reanalysis of data from the James Webb Space Telescope (JWST) shows that these black holes could have been present during the first 50 million years of our 13.8 billion year old universe, driving star formation at such an early age .
The results could challenge the idea that only black holes were created after the first stars and galaxies emerged.
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“We know that these monster black holes are in the center of galaxies near our Milky Way, but the big surprise now is that they were also present at the beginning of the universe and that they were almost like blocks building blocks or seeds for early galaxies,” Joseph Silk, team leader and professor at Johns Hopkins University, said in a statement. “They gave a lot of everything, like huge amplifiers of star formation, which is the whole of what we thought could be before – so much so that this could our understanding of how galaxies form to be completely shaken.”
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Silk points out that distant and early galaxies that the JWST has been looking at, since it began sending data to Earth in the summer of 2022, are brighter than expected.
This suggests that the galaxies are already filled with unusually high numbers of stars and supermassive black holes; if true, it would mean that our current theories about how galaxies grow may need to be revised.
“We argue that a black hole ejects clouds of compressed gas, turning them into stars and greatly accelerating the rate of star formation,” Silk said. “Other than that, it’s very difficult to understand where these bright galaxies came from because they are typically smaller in the early universe. Why on earth should they be making stars so fast?”
Currently, the most widely accepted theories of cosmic evolution suggest that the universe’s black holes were born early when very massive stars exhausted their supplies of the fuel needed for nuclear fusion. Afterwards, those stars would have collapsed and created black holes in the later epochs of the universe. This means that the black holes would have to come after the formation of the stars that gave birth to them, as well as before the first gathering of galaxies.
However, Silk and his colleagues found that black holes and galaxies appear to have coexisted during the ancient universe, impacting each other as early as 100 million years after the Big Bang. This period of time, says Silk, would only be equivalent to the first days of January if the history of the universe had been condensed into a calendar year.
It is soon crushing the universe
The massive gravitational influence of black holes means that nothing (not even light) can escape the outer boundary, known as the event horizon. What this means to us is that whatever is outside that boundary cannot be seen directly.
But beyond the event horizon, things still happen. A black hole’s gravity is still intense enough to generate violent conditions for any surrounding matter as the abyss falls too close to the event horizon, heating it and causing it to flow brightly. This material can be swallowed, or it can be directed to the poles of the black hole, where it is blasted out at near-light speeds as jets or winds.
Black holes actively feeding on such matter can power what are called active galactic nuclei (AGN), or regions within galaxies that can emit the combined light of all the stars in the galaxies themselves.
Silk thinks that what makes black holes “cosmic particle accelerators” in this way is what allowed the JWST to see so many early in the universe.
“We can’t see these violent winds or jets from far, far away, but we know they must be there because we see a lot of black holes early in the universe,” Silk explained. “These massive winds coming from the black holes create the nearby gas clouds and turn them into stars. That’s the missing link that explains why these first galaxies are so much brighter than expected we.”
The universe was going through a phase (or two)
The team behind this research theorized that the early universe had two distinct phases. High-velocity outflows from black holes would accelerate the birth of stars in the first stage. The second phase would have started when those outflows stopped.
Later, when the Universe was about a few hundred million years old, huge gas clouds would have collapsed through intense magnetic storms caused by supermassive black holes. This ushered in a new period of intense, rapid star formation that far exceeded the star birth rates seen in more modern galaxies.
Star formation would then be blocked because massive outflows from supermassive black holes would have transitioned into an energy-conserving state, cutting off the supply of gas in galaxies that could host stars.
“We originally thought that galaxies formed when a giant gas cloud collapsed,” Silk explained. “The big surprise is that there was a seed in the middle of that cloud – a big black hole – and that quickly helped turn the inner part of that cloud into stars at a much greater rate than we expected ever. And so of the first galaxies they are extremely bright.”
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Not only does the team think that future JWST data could provide a more accurate count of early stars and supermassive black holes that will confirm the new theory, but the researchers also believe that the $10 billion space telescope can provide some answers to fundamental questions found closer to home.
“The big question is, what was our beginning? The sun is one star in 100 billion in the Milky Way galaxy, and there is a massive black hole sitting in the middle, too. What is the connection between the two?” Finished Silk. “Within a year, we will have much better data and begin to get answers to many of our questions.”
The team’s research was published in January in the Astrophysical Journal Letters.
