A supermassive black hole takes a long time to grow, even if it eats voraciously. Therefore, figuring out how supermassive black holes that are billions of times heavier than the sun formed in the first billion years of the universe’s life has been an ongoing mystery.
But new work by an international team of cosmologists suggests an answer: streams of cold matter, made up of mysterious dark matter, fuel black holes born from the death of giant primordial stars.
“There is a recipe for creating a 100,000 solar mass black hole at birth, a 100,000 solar mass primordial star,” said Daniel Wallen, a cosmologist at the University of Portsmouth. independent. “In the current universe, the only black holes that we have all discovered were formed from the collapse of massive stars. This means that the minimum mass of a black hole must be at least three or four solar masses.”
But the gap is huge between a star of 4 solar masses and a star of 100,000 solar masses, which would be a “giant” star if centered around the Sun to extend into the orbit of Pluto. In the past 20 years, according to Dr. Wallen, much of the research on quasars in the early universe — the centers of extremely bright galaxies powered by supermassive black holes — has focused on the finely tuned set of conditions that would allow the formation of such quasars. A huge primitive star.
But in a new article published in the magazine temper natureWallen and colleagues used a supercomputer model of cosmic evolution to show that rather than evolving from a very special set of conditions, primordial giant stars form and collapse into quasars “seeds” quite naturally from a set of initial conditions that, although still relatively rare, However, it is much less sensitive. And it all starts with dark matter.
“If you look at the total content, let’s call it the energy content of the total mass of the universe, 3 percent in the form of matter we understand,” explained Dr. Wallen — a substance made up of protons, neutrons, electrons, hydrogen, helium and more. But “24 percent is in the form of dark matter, and we know it’s there because of the movement of galaxies and galaxy clusters, but we don’t know what it is.”
That is, dark matter appears to only interact with ordinary matter through gravity, and it is the gravity of dark matter that has created the largest structure in the universe: the cosmic web. According to Dr. Wallen, in the early universe, large swaths of dark matter collapsed into long filaments under their own weight and dragged normal matter with it, forming a network of filaments and their junctions.
Galaxies and stars eventually form within the filaments, and in particular, at the matter-rich intersections of the filaments.
Dr. Wallen stressed the intersections, saying, “We call them halos, cosmic halos, and we think primordial stars formed there first.”
Previous ideas were that in order to form a primordial star large enough to give birth to a supermassive black hole and create a quasar in the first billion years of the universe, the corona would have to grow to gigantic proportions under special conditions: there are no other stars so close, this hydrogen has formed molecular to keep the gas cool, and those supersonic flows of gas kept the corona turbulent. As long as the aura was cold and turbulent enough, it wouldn’t be able to hold together enough to ignite like a star, prolonging its growth phase until it was finally born of gigantic size.
Dr. Wallen noted that once a massive star ignites, lives its life, deflates and collapses into a black hole, it should have access to large amounts of gas to grow exponentially, “because the way a black hole grows swallows gas.”
But rather than requiring extremely narrow conditions for supermassive star formation and eventually a supermassive black hole, Dr. Wallen and colleagues’ simulations suggest that the flow of cold gas into a halo of filaments defined by dark matter in the cosmic web could replace many of the factors needed for primordial star formation in models. Old.
“Si los flujos de acreción fríos están alimentando el crecimiento de estos halos, deben estar golpeando esos halos”, dijo el Dr. Whalen, “golpeándolos con tanto gas tan rápidamente, que la turbulencia podría estar impidiendo que el gas colapse y form una estrella is very important.”
When they simulated such a corona fed by cold accretion streams, the researchers saw two massive protostars forming, one the size of 31,000 suns, and the other the size of 40,000 suns. Supermassive black hole seeds.
“It was wonderfully simple. The 20-year problem disappeared overnight. When there are cold streams pumping gas in a halo into the cosmic web,” Dr. Wallen noted, “there would be so much turbulence that massive star formation and massive seed formation would occur. It results in a giant quasar seed.”
He added that it is a discovery that matches the number of quasars seen so far in the early universe, noting that large halos at that early time are rare, as well as quasars.
But the new work is a simulation, and the scientists would like to actually monitor the formation of quasars from the early universe in nature. New instruments like the James Webb Space Telescope may make this a reality relatively soon.
“The web will be strong to see one,” Dr. Wallen said, possibly to see the birth of black holes within a million or two million years of the Big Bang.