Scientists have discovered the secret of the birth of the oldest black holes in the universe

Scientists have discovered the secret of the birth of the oldest black holes in the universe

It takes a long time for a supermassive black hole to grow, even if it eats voraciously. So how supermassive black holes that are billions of times heavier than the sun formed during the first billions of the universe’s life has always been a mystery.

But new work by an international team of cosmologists suggests an answer: Streams of cold matter, formed by mysterious dark matter, feed black holes with a force born from the death of giant protostars.

“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 universe today, the only black holes that we have discovered, they are all formed from the collapse of massive stars. This means that the minimum mass of a black hole must be at least three to four solar masses.”

But the bay is huge between a star of mass 4 solar masses and a star of mass of 100,000 solar masses, a “giant” star that, if centered around the sun, would extend into the orbit of Pluto. Dr. Wallen said that over the past 20 years, much of the research on quasars in the early universe — centers of very bright galaxies powered by supermassive black holes — has focused on the finely tuned set of conditions that would allow for the formation of such a massive primordial star.

But in a new paper published in the journal temper natureWallen and colleagues used supercomputer modeling of cosmic evolution to show that rather than evolving from a very special set of conditions, extremely giant protostars form and collapse into quasars “seeds” quite naturally from a set of primordial conditions that, although still rare, Relatively speaking, it is much less sensitive. And it all starts with dark matter.

“If you look at the total content, let’s call it the total mass energy content of the universe, 3 percent of it in the form of matter we understand” – a substance made of protons, neutrons, electrons, hydrogen, helium and so on, Dr. Wallen said. 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.”

This means that dark matter only interacts with ordinary matter through gravity, and it is the gravity of dark matter that has created the largest structure of the universe: the cosmic web. Dr. Wallen said that in the early universe, vast swathes of dark matter collapsed into long filaments under their own weight, dragging normal matter with it, forming a web of filaments and their junctions.

Galaxies and stars eventually form within the filaments, and in particular, the matter-rich intersections of the filaments.

“We call them halos, cosmic halos, and we think primordial stars formed there first,” Dr. Wallen said of the intersections.

Previous thinking believed that to form a primordial star large enough to give birth to a supermassive black hole and create a quasar during the first billion years of the universe, the corona would need to grow to gigantic proportions under special conditions: no other stars so close, forming molecular hydrogen in order to sustain Gas cooler, supersonic gas flows to keep the corona turbulent. As long as the aura was cold and turbulent enough, it couldn’t hold together enough to ignite like a star, prolonging its growth phase until it was finally born of gigantic size.

Once a massive star ignites, lives its life, burns up, and collapses into a black hole, Dr. Wallen said, it must have access to large amounts of gas in order to grow exponentially, “because the way a black hole grows is to swallow gas.”

But rather than requiring finely-tuned conditions for the formation of a supermassive star and eventually a supermassive black hole, Dr. Wallen and colleagues’ simulations suggest that the flow of cold gas into a halo of dark matter filaments defining the cosmic web could replace the abundance. A necessary factor for the formation of primordial stars in ancient models.

“If cold accretion fluxes are fueling the growth of these halos, they must be bombarding those halos,” Dr. Wallen said, hitting them with so much gas so quickly that turbulence might prevent the gases from collapsing and forming a primordial star. “

When they simulated such a corona fed by cold accretion streams, the researchers observed the formation of two massive primordial stars, one the size of 31,000 suns, and the other the size of 40,000 suns. Supermassive black hole seeds.

“It was beautifully simple. The 20-year problem was over overnight,” Dr. Wallen said. Anytime you have cold streams pumping gas in a halo into the cosmic web, “You’re going to have a lot of turbulence, and you’re going to have massive star formation and massive seed formation.” It produces a huge quasar seed.”

He added that it is a discovery that matches the number of quasars observed so far at the beginning of the universe, noting that large halos in that early era are rare, as well as quasars.

But the new work is a simulation, and the scientists then want to actually monitor the formation of the early quasar universe in the wild. New instruments, such as the James Webb Space Telescope, may make that a reality relatively soon.

“Webb would be strong to see one,” Dr. Wallen said, and probably watched the birth of black holes within a million or two million years of the Big Bang.

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