The early universe contained much less miniature black holes than previously thought, making the origin of the missing matter in our cosmos an even bigger mystery, a new study suggests.
Miniature or primordial black holes (PBHs) are black holes that are believed to have formed in the first fractions of a second after the Big Bang. According to leading theories, these dime-sized singularities formed from rapidly collapsing regions of thick, hot gas.
Many physicists explain the universe’s dark matter, a mysterious entity that, despite being completely invisible, makes the universe much more massive than can be explained by the matter we see.
But even though the hypothesis is popular, there is one major problem: we have not yet been able to directly observe any primordial black hole. Now a new study has offered a possible explanation for why they haven’t formed, opening cosmology’s dark matter problem to wider speculation.
According to the study, the modern universe could have taken shape with far fewer pristine black holes than previous models had estimated. The researchers published their findings in the journal on May 29 Physical Assessment Letters.
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‘Many researchers think so [primordial black holes] are a strong candidate for dark matter, but there should be enough of them to fit that theory,” says lead author Jason Kristianoa graduate student in theoretical physics at the University of Tokyo, said in a statement. ‘They are also interesting for other reasons, as since the recent innovation of gravitational wave astronomy there have been discoveries of binary black hole mergers, which can be explained if PBHs occur in large numbers. But despite these strong reasons for their expected abundance, we haven’t seen any directly, and now we have a model that should explain why this is the case.”
There is a hole in the photo
The universe began 13.8 billion years ago with the Big bangcausing the young cosmos to explode outwards due to an invisible force known as dark energy.
As the universe grew, ordinary matter, interacting with light, solidified around clumps of invisible matter dark matter to create the first galaxies, connected by a vast cosmic web. Today, cosmologists think that ordinary matter, dark matter, and dark energy make up about 5%, 25%, and 70% of the universe’s composition, respectively.
Initially, the universe was opaque, a plasma fluid through which no light could pass without being ensnared by electromagnetic fields produced by moving charges. But after 380,000 years of cooling and expansion, the plasma eventually recombined into neutral matter, releasing microwave static electricity that became the universe’s first light: the cosmic microwave background (CMB).
Cosmologists have been looking for these early black holes by studying this first baby photo of the universe. Yet no one has been found so far.
Some physicists think it’s possible they haven’t yet discovered the vast numbers of pristine black holes needed to explain dark matter simply because they have yet to learn how to detect them.
But by applying a model based on an advanced form of quantum mechanics, quantum field theory, to the problem, the researchers behind the new study came to a different conclusion: We can’t find primordial black holes because most of them simply aren’t . over there.
Primordial black holes are believed to have formed from the collapse of short but strong gravitational waves rippling through the universe. By applying their model to these waves, the researchers found that it takes far fewer of these waves to combine than other theories estimate to form larger structures in the universe. And the fewer waves needed to recreate the image, the fewer original black holes.
“It is widely believed that the collapse of short but strong wavelengths in the early universe caused the formation of primordial black holes,” says Kristiano. “Our study suggests that there should be far fewer PBHs than would be necessary if they are indeed a strong candidate for dark matter or gravitational wave events.”
To confirm their theory, the researchers will look to future, hypersensitive gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA) Projectto be launched into space in 2035 on an Ariane 3 rocket.