More than 13 billion years after they formed, distant massive black holes from the early universe are revealing themselves. The light that was released to create them is now reaching our telescopes.
But that left scientists with a conundrum: How did they form so quickly when the universe was young? Black holes take time to form. Typically, a massive star has to burn through all of its fuel, explode into a supernova and create a black hole. Massive black holes take even longer.
What if these black holes formed differently? A research team comprised of scientists from multiple universities believes that these very massive black holes were created when galaxies formed very quickly and violently. So rather than forming stars, that normal process was disrupted and led to black hole formation, according to a new study published in the journal Nature on Wednesday.
Previously, scientists believed that massive black holes could only form in regions that were full of intense, ultraviolet star-killing radiation from nearby galaxies. This turns that notion on its head, putting massive black holes in starless regions that grew rapidly.
But how does this process actually work? It relies on the gas clouds that lead to galaxy creation, said John Wise, study co-author and associate professor at the Georgia Institute of Technology’s School of Physics.
“In this study, we have uncovered a totally new mechanism that sparks the formation of massive black holes, in particular dark matter halos,” Wise said. “Instead of just considering radiation, we need to look at how quickly the halos grow. We don’t need that much physics to understand it — just how the dark matter is distributed and how gravity will affect that. Forming a massive black hole requires being in a rare region with an intense convergence of matter.”
Dark matter, the key unseen ingredient of the universe, collapsed into halo-like formations that grew rapidly, preventing star formation. That flow of gaseous matter was the fuel the black holes needed to form.
“The violent and turbulent nature of the rapid assembly, the violent crashing together of the galaxy’s foundations during the galaxy’s birth prevented normal star formation and led to perfect conditions for black hole formation instead,” said John Regan, study co-author and research fellow at Dublin City University’s Centre for Astrophysics and Relativity. “This research shifts the previous paradigm and opens up a whole new area of research.”
To make this discovery, the researchers’ understanding of the evolution of the early universe came from a 70-terabyte data set called the Renaissance Simulation suite created on the Blue Waters supercomputer. In the data, they found 10 dark matter halos where stars should have formed, but only gas clouds existed.
They used the Stampede2 supercomputer to zoom in on the simulations of two of the halos and travel back in time to see what was happening in them about 270 million years after the Big Bang. This allowed them to see the formation of the black holes — matter forming, gas inflowing, turbulence, condensing and the spinning motion.
“It was only in these overly-dense regions of the universe that we saw these black holes forming,” Wise said. “The dark matter creates most of the gravity, and then the gas falls into that gravitational potential, where it can form stars or a massive black hole.”
In addition, this discovery also led the researchers to find that black holes are even more common throughout the universe than previously thought.
“An exciting component of this work is the discovery that these types of halos, though rare, may be common enough,” said Brian O’Shea, study co-author and professor at Michigan State University’s department of physics and astronomy. “We predict that this scenario would happen enough to be the origin of the most massive black holes that are observed, both early in the universe and in galaxies at the present day.”
In the future, these simulations could also show the lifespan of massive black holes, focusing on how they grow and evolve over time.
“Where are these black holes today? Can we detect evidence of them in the local universe or with gravitational waves?” Regan said. “Our next goal is to probe the further evolution of these exotic objects.”