Scientists may have finally solved the problem of the universe’s 'missing' black holes

The early universe contained far fewer miniature black holes than previously thought, making the origins of our cosmos's missing matter an even greater mystery, a new study has suggested.

Miniature, or primordial, black holes (PBHs) are black holes thought to have formed in the first fractions of a second after the Big Bang. According to leading theories, these dime-sized singularities popped into existence from rapidly collapsing regions of thick, hot gas.

The pockets of infinitely dense space-time are how many physicists explain the universe's dark matter, a mysterious entity that, despite being completely invisible, makes the universe much heavier than can be explained by the matter we see. 

But even though the hypothesis is popular, it has one big problem: we've yet to directly observe any primordial black holes. Now, a new study has offered a possible explanation as to why they didn't form, throwing open cosmology's dark matter problem to wider speculation. 

According to the research, the modern universe could have taken shape with far fewer primordial black holes than previous models estimated. The researchers published their findings May 29 in the journal Physical Review Letters.

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"Many researchers feel they [primordial black holes] are a strong candidate for dark matter, but there would need to be plenty of them to satisfy that theory," lead author Jason Kristiano, a graduate student in theoretical physics at the University of Tokyo, said in a statement. "They are interesting for other reasons too, as since the recent innovation of gravitational wave astronomy, there have been discoveries of binary black hole mergers, which can be explained if PBHs exist in large numbers. But despite these strong reasons for their expected abundance, we have not seen any directly, and now we have a model which should explain why this is the case."