The small primordial but undetectable black holes could be one of the mysterious sources of mass that contribute to dark matter. There are significant limits to their lifespan in open space, but in recent years, astrophysicists have wondered: what if these black holes are in the core of neutron stars?
Gradually, such black holes will accumulate the neutron star, devouring it from within. These hypothetical systems are not yet verified, but a new prepress work, published on arXiv and not yet evaluated by colleagues, calculated how long this devour would take.
This, in turn, could be used to analyze the current population of neutron stars to constrain the nature of black holes as a candidate for dark matter – whether they are primordial, dating from the Big Bang, or black holes that have formed inside neutron stars.
Although we do not know what dark matter is, it is quite fundamental to understanding the Universe: there is simply not enough matter that we can detect directly – normal matter – to explain all gravity. In fact, there is so much gravity that scientists have calculated that about 75 to 80 percent of all matter is dark.
There are a number of candidate particles that could be dark matter. The primordial black holes that formed immediately after the Big Bang are not one of the leading candidates, because if they were over a certain table, we would have noticed them by now; but under that mass, it would have evaporated by emitting Hawking radiation long before now.
However, black holes are an attractive candidate for dark matter: and they are extremely difficult to detect if they are just sitting in space doing nothing. So astronomers keep looking for them.
A recently explored idea is the endoparasitic black hole. There are two scenarios for this. One is that the primordial black holes were captured by neutron stars and sank to the core. The other is that particles of dark matter are captured inside a neutron star; if conditions are favorable, they could then merge and collapse into a black hole.
These black holes are small, but they wouldn’t stay that way. From their comfortable position, embedded inside the neutron star, these small black holes would parasitize their host.
The team of physicists at Bowdoin College and the University of Illinois at Urbana-Champaign calculated the accumulation rate – the rate at which the black hole would devour the neutron star – for a range of mass ratios of black holes, from three to nine orders. less massive in size than the neutron star’s host.
Neutron stars have a theoretical upper mass limit 2.3 times higher than the Sun’s mass, so that the masses of black holes would extend into the range of dwarf planets.
For a neutron star that does not rotate and hosts a non-rotating black hole, the accretion would be spherical. At the team’s calculated accumulation rates, black holes up to 10-21 whenever the mass of the Sun would completely accumulate a neutron star during the life of the Universe.
This suggests that primordial black holes, from the beginning of the Universe, would have fully accumulated their host neutron stars by now. These time periods are in direct conflict with the ages of old populations of neutron stars, the researchers said.
“As an important application, our results confirm the arguments that use the current existence of neutron star populations to constrain either the contribution of primordial black holes to the dark matter content of the Universe or that of dark matter particles that can form black holes at the center. neutron stars after they have been captured, “they wrote in their paper.
So the result is another blow to the primordial black holes; but does not completely rule out endoparasitic black holes. If there are globes of dark matter particles floating in space and thrown into neutron stars, they could collapse into black holes and turn neutron stars into black holes even when you read this sentence.
And that’s weird.
The team’s work was published on arXiv.