James Webb Space Telescope reveals surprising evolution in black hole and galaxy formation: ScienceAlert
The beginning of the universe has always been a chicken-and-egg problem. Did stars and galaxies form first, with black holes slowly merging in their centre? Or did black holes appear before the first galaxies?
As matter began to cool and collect after the Big Bang, it arranged itself into the shapes and objects we observe throughout most of its 13.8 billion-year history. Today we see these objects as stars clustered in gravitationally bound systems we call galaxies, which orbit a supermassive black hole at their center.
Traditionally, it was assumed that stars and galaxies were here first. But a new analysis of data from the early universe collected by the James Webb Space Telescope suggests that black holes and galaxies appeared together, and that black holes shaped the galaxies that evolved around them.
“We know that these massive black holes exist in the centers of galaxies close to our own Milky Way, but the biggest surprise now is that they were present in the early universe as well and were almost like building blocks or seeds for early galaxies,” he says. Astronomer Joseph Silk from Johns Hopkins University in the United States and the Sorbonne University in France.
“They’ve really boosted everything, like giant megaphones of star formation, which is a complete reversal of what we thought was possible before — so much so that this could completely shake our understanding of how galaxies form.”
There’s a lot we don’t know about the early universe, for the simple reason that we can’t see it. When matter first began accumulating during the first 500 million to 1 billion years after the Big Bang, a thick fog of gases between stars and galaxies made space opaque.
We thought we had a fairly decent handle on things. But then, in the last decade or so, we started finding things that didn’t fit the model that scientists had built. Such as black holes and galaxies that were much larger than we thought could have formed sometime after the Big Bang. When the James Webb Space Telescope appeared, it showed that there were many more of these large objects, observed even earlier, than we had imagined.
Supermassive black holes are a particular problem, because of the way some black holes form from stars. When a particularly large star dies, its core collapses, leaving a black hole about 50 times the mass of the Sun.
More massive black holes can form from collisions between these objects, but supermassive black holes have a mass of millions to billions of times the mass of the Sun. If these objects were forming from the ground up, it would take a very long time, and the stars would have to be there first.
James Webb Space Telescope data reveal the existence of supermassive black holes very early in the history of the universe. We have observed giant organisms less than 500 million years after the Big Bang, one at 470 million years, and another at 400 million years; Interestingly, the mass of the latest black hole, which is about 1.6 million suns, appears to be equal to the mass of the small galaxies orbiting it.
This strongly suggests that there is another mechanism for black hole formation: massive clouds of matter collapse directly into black holes without becoming stars in the first place.
According to the analysis by Silk and his team, this means they could have been around very early, coexisting with the nascent galaxy and stimulating its growth. As the central part of the cloud collapsed into a black hole, the remaining edges of the cloud became the material needed to form young stars.
This is because the black hole feeding process triggers powerful winds and jets of high-speed plasma that tear apart the surrounding space, compressing the star-forming gas in it and triggering intense waves of star formation.
“We argue that the black hole flows outward from crushed gas clouds, turning them into stars and dramatically accelerating the rate of star formation,” Silk says.
“We can’t see these violent winds or jets far away, but we know they must be there because we see so many black holes in the early universe.”
Future observations should help astronomers determine the accuracy of this model and improve it further.
But now, it’s starting to look like the chicken-or-the-egg problem is an oversimplification: it’s not one or the other, but both together, turning the soup of the early universe into a glorious collection of galaxies, each powered by forces of energy. A black hole streaks across the universe as far as we can see.
The research was published in Astrophysical Journal Letters.