Small, anything but undetectable primordial black holes can be one of the mysterious mass sources that contribute to dark matter. There are significant limits to their lifespan in open space, but in recent years astrophysicists have asked: what if these black holes are in the nucleus of neutron stars?
Gradually, such black holes will adorn the neutron star and consume it from within. These hypothetical systems have yet to be verified, but a new preprint article, published on arXiv and yet to be judged by peers, has calculated how long this devastation would take.
This in turn could be used to analyze the current population of neutron stars to limit the nature of the black holes considered a candidate for dark matter – whether it is original, dating from the big bang or black holes which formed in neutron stars.
Although we do not know what dark matter is, it is very important for our understanding of the universe: there is simply not enough matter that we can detect directly – normal matter – to take into account all seriousness. In fact, there is so much gravity that scientists have calculated about 75 to 80 percent of all matter is dark.
There are a number of candidate particles that can be dark matter. Older black holes formed just after the big bang are not one of the leading candidates, because if they were above a certain mass, we would have noticed them by now; but under that mass they would have evaporated long before by the Hawking radiation.
However, black holes are an attractive candidate for dark matter: it is also very difficult to detect if they are just hanging around in space and doing nothing. So astronomers are still searching for them.
One idea that has been recently investigated is the endoparasitic black hole. There are two scenarios for this. One is that primordial black holes are captured by neutron stars and sink into the nucleus. The other is that dark matter particles are trapped in a neutron star; if the conditions are favorable, it can come together and fall into a black hole.
These black holes are small, but they will not stay that way. From their cozy location, enclosed in the neutron star, these little black holes will parasitize their host.
The team of physicists from Bowdoin College and the University of Illinois at Urbana-Champaign calculated the growth rate – that is, the rate at which the black hole would devour the neutron star – for a series of mass ratios of black holes, from three to nine. orders of magnitude less massive than the neutron star host.
Neutron stars have a theoretical upper mass limit of 2.3 times the mass of the sun, so the black hole masses will extend into the series of dwarf planets.
For a non-rotating neutron star that presents a non-rotating black hole, the accretion will be spherical. According to the team’s calculation increase, black holes are as small as 10-21 times the mass of the sun would accumulate a neutron star completely within the lifetime of the universe.
This suggests that primordial black holes, from the beginning of the universe, would have completely adorned their host neutron stars before. These time scales are in direct conflict with the ages of the population of ancient neutron stars, 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 primary black holes to the dark matter content of the universe, or that of dark matter particles forming black holes at the center of neutron stars after being captured, ”they wrote in their paper.
The result is therefore another blow to primeval-black holes; but it does not exclude endoparasitic black holes. If there are light bulbs there are dark matter particles floating through space and thrown into neutron stars, they can collapse into black holes and turn neutron stars into black hole conversions, even if you read this sentence.
And it’s terribly freaking.
The team’s paper was published on arXiv.