UCLA researchers propose a groundbreaking theory suggesting that dark matter played a crucial role in the formation of supermassive black holes in the early universe, offering a solution to a long-standing cosmic puzzle.
A team of UCLA astrophysicists has proposed a remarkable theory to explain the existence of supermassive black holes in the early universe, a mystery that has perplexed scientists for decades. Their study, published in the journal Physical Review Letters, suggests that dark matter may have played a crucial role in the formation of these colossal cosmic giants far earlier than previously thought possible.
Supermassive black holes, like the one at the center of our Milky Way galaxy, typically form over billions of years. These monstrous entities, some with masses billions of times that of our sun, are thought to arise from the gradual accumulation of gas and stars and through black hole mergers. Yet, the James Webb Space Telescope has been detecting supermassive black holes that seem to have formed during the universe’s infancy, presenting a paradox to conventional astrophysical theories.
“How surprising it has been to find a supermassive black hole with a billion solar mass when the universe itself is only half a billion years old,” Alexander Kusenko, a professor of physics and astronomy at UCLA and senior author of the study, said in a news release. “It’s like finding a modern car among dinosaur bones and wondering who built that car in the prehistoric times.”
This enigmatic discovery has compelled researchers to look beyond traditional explanations. Some scientists have suggested that a vast cloud of gas might directly collapse into a supermassive black hole, bypassing the lengthy process of stellar evolution and mergers. However, the rapid cooling of gas clouds typically leads to their fragmentation into smaller objects, preventing the formation of large black holes.
“How quickly the gas cools has a lot to do with the amount of molecular hydrogen,” Yifan Lu, the study’s first author and a doctoral student at UCLA, said in the news release. “[H]ydrogen molecules become cooling agents as they absorb thermal energy and radiate it away. Hydrogen clouds in the early universe had too much molecular hydrogen, and the gas cooled quickly and formed small halos instead of large clouds.”
By venturing into uncharted territory, Lu, along with postdoctoral researcher Zachary Picker, identified a possible solution. They developed simulations incorporating additional radiation that influences the cooling of gas clouds. This radiation, they found, could disrupt molecular hydrogen and prevent the gas from cooling too fast, thereby allowing large clouds to form and eventually collapse into supermassive black holes.
“If you add radiation in a certain energy range, it destroys molecular hydrogen and creates conditions that prevent fragmentation of large clouds,” Lu added.
But what could be the source of this critical radiation?
Their answer points toward dark matter, an elusive form of matter that constitutes a significant portion of the universe. While dark matter has been detected through its gravitational influence, its exact nature remains unknown. The researchers speculate that dark matter could consist of unstable particles that decay into photons — particles of light that could generate the necessary radiation to keep hydrogen clouds sufficiently warm to prevent fragmentation.
“This could be the solution to why supermassive black holes are found very early on,” added Picker. “If you’re optimistic, you could also read this as positive evidence for one kind of dark matter. If these supermassive black holes formed by the collapse of a gas cloud, maybe the additional radiation required would have to come from the unknown physics of the dark sector.”
This theory not only provides a plausible explanation for the formation of early supermassive black holes but also hints at a new interaction between dark matter and ordinary matter. Such an interaction could revolutionize our understanding of the cosmos and open new avenues for exploring the properties of dark matter.
As astrophysicists continue to unravel the mysteries of the early universe, this study represents a monumental step forward in understanding how some of the oldest and most massive objects in existence came to be. The intriguing role of dark matter in this cosmic saga underscores the complexity and wonder of the universe, reminding us that many of its secrets have yet to be uncovered.