March 1, 2024

Which came first: black holes or galaxies?

An illustration of a magnetic field generated by a supermassive black hole in the early universe, showing turbulent flows of plasma that turn gas clouds into stars. Credit: ROBERTO MOLAR CANDANOSA/JHU

Black holes not only existed at the dawn of time, they also gave rise to new stars and the formation of supercharged galaxies, a new analysis of data from the James Webb Space Telescope suggests.

The insights upend theories about how black holes shape the cosmos, challenging the classical understanding that they formed after the first stars and galaxies emerged. Instead, black holes may have dramatically accelerated the birth of new stars during the Universe’s first 50 million years, a fleeting period in its 13.8 billion-year history.

“We know that these monstrous black holes exist at the centers of galaxies close to our Milky Way, but the big surprise now is that they were also present in the early Universe and were almost like building blocks or seeds for the first galaxies,” said lead author Joseph Silk, professor in the Department of Physics and Astronomy at Johns Hopkins University and the Paris Institute of Astrophysics, Sorbonne University. “They really boosted everything, like gigantic amplifiers of star formation, which is a complete turnaround from what we thought was possible before – so much so that it could completely shake up our understanding of how galaxies form.”

The work was recently published in Astrophysical journal letters.

Distant galaxies from the early universe observed through the Webb telescope appear much brighter than scientists predicted and reveal unusually high numbers of young stars and supermassive black holes, Silk said.

Conventional wisdom holds that black holes formed after the collapse of supermassive stars and that galaxies formed after the first stars illuminated the dark early universe. But Silk’s team’s analysis suggests that black holes and galaxies coexisted and influenced each other’s fates for the first 100 million years. If the entire history of the universe were a 12-month calendar, those years would be like the first days of January, Silk said.

“We are arguing that the black hole releases crushed gas clouds, turning them into stars and greatly accelerating the rate of star formation,” Silk said. “Otherwise, 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 forming stars so quickly?”

Black holes are regions of space where gravity is so strong that nothing can escape its pull, not even light. Because of this force, they generate powerful magnetic fields that trigger violent storms, ejecting turbulent plasma and, ultimately, acting as huge particle accelerators, Silk said. This process, he said, is likely why Webb’s detectors have detected more black holes and bright galaxies than scientists predicted.

“We can’t see these violent winds or jets far, far away, but we know they must be present because we see a lot of black holes in the early Universe,” Silk explained. “These huge winds from black holes crush nearby gas clouds and turn them into stars. That’s the missing link that explains why these first galaxies are so much brighter than we expected.”

Silk’s team predicts that the young universe had two phases. During the first phase, high-speed outflows from black holes accelerated star formation, and then, in a second phase, the outflows slowed down. A few hundred million years after the big bang, gas clouds collapsed due to magnetic storms from supermassive black holes, and new stars were born at a rate far exceeding that seen billions of years later in normal galaxies, Silk said. Star creation has slowed because these powerful outflows have transitioned to an energy-conserving state, he said, reducing the gas available to form stars in galaxies.

“We originally thought that galaxies formed when a giant cloud of gas collapsed,” explained Silk. “The big surprise is that there was a seed in the middle of that cloud – a big black hole – and that helped rapidly turn the inner part of that cloud into stars at a much greater rate than we ever expected. They’re incredibly bright.”

The team hopes that future observations from the Webb telescope, with more accurate counts of stars and supermassive black holes in the early universe, will help confirm their calculations. Silk hopes these observations will also help scientists gather more clues about the evolution of the universe.

“The big question is: What were our beginnings? The sun is one star in 100 billion in the Milky Way galaxy, and there’s a huge black hole in the middle too. What’s the connection between the two?” he said. “Within a year we will have much better data and many of our questions will begin to receive answers.”

Authors include Colin Norman and Rosemary FG Wyse of Johns Hopkins; Mitchell C. Begelman of the University of Colorado and the National Institute of Standards and Technology; and Adi Nusser of the Israel Institute of Technology.

More information:
Joseph Silk et al, Which Came First: Supermassive Black Holes or Galaxies? JWST information, The letters from the astrophysical journal (2024). DOI: 10.3847/2041-8213/ad1bf0

Provided by Johns Hopkins University

Quote: What came first: black holes or galaxies? (2024, February 10) retrieved February 10, 2024 from https://phys.org/news/2024-02-black-holes-galaxies.html

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