July 25, 2021

The mysterious dark matter is not made from black holes – The Province

The mysterious dark matter is not made from black holes - The Province


Physicists at UC Berkeley have dismissed the possibility that the mysterious dark matter of the universe could consist of a fullness of black holes scattered throughout the universe, against speculation after the detection of gravitational waves.

Based on a statistical analysis of 740 of the brightest supernovae discovered since 2014, and the fact that none of them seems to be magnified or illuminated by "gravitational lenses" of hidden black holes, the researchers concluded that primordial black holes do not they can compensate more than about 40% of the dark matter in the universe.

Thus, primordial black holes could only have been created within the first milliseconds of the Big Bang as regions of the universe with a concentrated mass tens or hundreds of times greater than that of the sun, collapsed into objects 100 kilometers wide.

The results suggest that none of the dark matter in the universe consists of heavy black holes, or any similar object, including massive compact halo objects, called MACHOs. The analysis is detailed in an article published this week in the journal Physical Review Letters.

Dark matter is one of the most embarrassing enigmas of astronomy: Although it comprises 84.5% of the matter in the universe, no one can find it. The candidates proposed for dark matter cover almost 90 orders of magnitude in mass, from ultralight particles such as axions to MALE.

Several theorists have proposed scenarios in which there are multiple types of dark matter. But if dark matter consists of several unrelated components, each would require a different explanation for its origin, which makes the models very complex.

"I can imagine that there are two types of black holes, very heavy and very light, or black holes and new particles, but in that case, one component is orders of magnitude heavier than the other, and they must be produced in comparable abundance. We would go from something astrophysical to something really microscopic, maybe even the lightest thing in the universe, and that would be very difficult to explain, "said lead author Miguel Zumalacárregui, of the Berkeley Center for Cosmological Physics.

A new analysis not yet published by the same team that uses a updated list of 1,048 supernovas reduces the limit by half, to a maximum of approximately 23%, and closes even more the door to the black hole-dark matter proposal.

"We're back to standard discussions, what is dark matter, in fact we're running out of good options," said Uro Seljak, professor of physics and astronomy at UC Berkeley. "This is a challenge for future generations"he assured.

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