Small, almost undetectable primal 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 nucleus of neutron stars?
Gradually, such black holes would grow and devour the neutron star from within. These hypothetical systems have yet to be verified, but a new prepress paper, published on arXiv and not yet peer-reviewed, has calculated how long this devouring would take.
This, in turn, could be used to analyze the current population of neutron stars to narrow down the nature of the black holes that are considered candidates for dark matter – whether they are primordial, dating back to the Big Bang, or black holes that formed in neutron stars. .
While we don’t know what dark matter is, it is quite fundamental to our understanding of the universe: there simply isn’t enough matter that we can directly detect – normal matter – to account for 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 can be dark matter. Primordial black holes that formed just after the Big Bang are not among the leading candidates, because if they had been above a certain mass we would have noticed them by now; but beneath that mass they would have evaporated long before through the emission of Hawking radiation.
However, black holes are an attractive candidate for dark matter: they are also extremely difficult to detect if they just hang in space and do nothing. So astronomers keep looking for them.
One idea that has recently been explored is the endoparasitic black hole. There are two scenarios for this. One is that original black holes were captured by neutron stars and sink to the core. The other is that dark matter particles are trapped in a neutron star; if conditions are right, they can converge and collapse into a black hole.
These black holes are small, but they wouldn’t stay that way. From their snug position nestled in the neutron star, these tiny black holes are said to be parasitizing their host.
The team of physicists from Bowdoin College and the University of Illinois at Urbana-Champaign calculated the accretion rate – that is, the rate at which the black hole would devour the neutron star – for a range of black hole mass ratios ranging from three to nine orders of magnitude which are less massive than the neutron star.
Neutron stars have a theoretical upper limit of mass of 2.3 times the mass of the sun, so the black hole’s mass would extend into the range of dwarf planets.
For a non-rotating neutron star harboring a non-rotating black hole, the accretion would be spherical. According to the team’s calculated accretion rates, black holes are as small as 10-21 times the mass of the sun a neutron star would grow completely within the lifetime of the universe.
This suggests that native black holes, from the beginning of the Universe, would have fully grown their host neutron stars until now. These timescales are in direct conflict with the ages of ancient neutron star populations, the researchers said.
“ As an important application, our results confirm arguments that use the current existence of neutron star populations to limit the contribution of native black holes to the content of dark matter in the Universe, or that of dark matter particles that can form black holes in the center of the Universe. neutron stars after being captured, ‘they wrote in their paper.
The result is thus another blow to primal black holes; but it doesn’t completely rule out endoparasitic black holes. If spheres of dark matter float through space and are absorbed into neutron stars, they could collapse into black holes and turn neutron stars into black holes, even if you read this sentence.
And that is really cool.
The team’s paper is published on arXiv.