Astronomers struggle to explain why ancient black holes are nowhere to be found

This theory could change our understanding of the early universe.

Black Magic

When the Big Bang gave birth to our universe 13.8 billion years ago, black holes were among the first things to emerge from this bubbling cauldron of hot, homogeneous matter. But it was somewhat different from the one we know today.

These ancient objects, known as primordial black holes, are thought to be incredibly small – perhaps the size of an atom – and extremely numerous. However, despite their crucial role in our understanding of the early universe, they remain hypothetical, as astronomers have never been able to find any in the cosmic microwave background (CMB), the remnants of the oldest light in the universe.

This threatens to create some holes in common cosmological models. Now, a team of researchers says they have an explanation, as detailed in a pair of… new studies: There may simply be far fewer primordial black holes than previously thought.

“Many researchers feel they are a strong candidate for dark matter, but there would have to be a lot of them to satisfy this theory,” said Jason Christiano, co-author of the studies and a graduate student at the University of Tokyo. a statement about job.

Despite the strong reasons for their abundance, he added, “we haven’t seen any of them directly, and now we have a model that should explain why this happens.”

Which makes waves

As Christian said, it’s tempting to believe that primordial black holes exist everywhere because they can precisely explain the existence of dark matter, the mysterious substance that accounts for more than 85% of the total mass in the universe.

Since black holes themselves are invisible and can only be observed through the influence of their gravity, it would be extremely difficult to detect primordial black holes of this small size. For these reasons, many astronomers believe that this is where all that dark matter could be hiding.

Then again, maybe not. According to the researchers, primordial black holes are created by the collapse of gravitational waves with short but powerful wavelengths. At the time they formed, shortly after the Big Bang, the universe was relatively young, allowing for the existence of these powerful waves that form black holes.

But by applying current understanding of quantum field theory to observations of the CMB, the researchers hypothesize that these waves, too, may not be as numerous as we thought.

“What we discovered is that these small but powerful waves can translate into the inexplicable amplification of much longer waves that we see in the current CMB,” said co-author Junichi Yokoyama of the Kavli Institute for Physics and Mathematics at the University of Tokyo. The universe is in the statement.

“While individual short waves would be relatively powerless, cohesive groups would have the ability to recreate waves much larger than themselves,” he added.

It’s a compelling theory, but we won’t get more definitive answers until we have gravitational wave observatories in space.

More about black holes: Scientists are trying to explain why hundreds of stars disappear from the night sky