The tiny, almost undetectable primordial black hole may be one of the mysterious mass sources of dark matter. Their life span in open space is greatly limited, but in recent years, astrophysicists have raised the question: What if these black holes are located in the core of a neutron star?
Such a black hole will gradually absorb the neutron star and swallow it from within. These hypothetical systems have yet to be verified, but a new preprint paper has been published on arXiv and is awaiting peer review. The paper has calculated the time to swallow.
In turn, this can be used to analyze the current total number of neutron stars to limit the properties of black holes that are considered candidates for dark matter-whether they are primitive black holes originating from the Big Bang, or black holes formed inside neutron stars.
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There are many possible candidate particles for dark matter. Primitive black holes formed just after the Big Bang are not one of the main candidates, because if they exceed a certain mass, we will notice them now. However, below this mass, they can already evaporate through the emission of Hawking radiation.
However, black holes are attractive candidates for dark matter: it is also very difficult for black holes to discover whether they are just wandering in space and doing nothing. Therefore, astronomers continue to search for them.
One idea that has been explored recently is the internal parasitic black hole. There are two options. One is that the original black hole is captured by the neutron star and sinks into the core. The other is that dark matter particles are trapped inside the neutron star. If conditions are favorable, they may merge into one and fall into a black hole.
These black holes are small, but they will not always be like this. From their comfortable position, lurking inside the neutron star, these small black holes will parasitize their host.
A team of physicists at Bowdoin College and the University of Illinois at Urbana-Champaign calculated the accretion rate, which is the rate at which a black hole can swallow a neutron star. The mass ratio of the black hole ranges from 3 to 9 orders of magnitude smaller than the mass of the neutron star.
The theoretical upper limit of a neutron star is 2.3 times the mass of the sun, so the mass of the black hole will extend down to the range of the dwarf planet.
For a non-rotating neutron star with a non-rotating black hole, its accretion will be spherical. According to the growth rate calculated by the team, the black hole is as small as 10-twenty one Twice the mass of the sun will completely absorb neutron stars during the lifetime of the universe.
This shows that from the beginning of the universe, primitive black holes have completely absorbed their host neutron stars. Researchers say these time scales directly conflict with the age of neutron stars.
“As an important application, our results confirm the use of the current existence of neutron star clusters to limit the contribution of primordial black holes to the dark matter content of the universe or the contribution of dark matter particles that may form black holes in the black hole. The center of the captured neutron star.” They wrote in the paper.
Therefore, the result is another blow to the original black hole. But this cannot completely eliminate the internal parasitic black hole. If there are clusters of dark matter particles floating in space and attracted to neutron stars, they may collapse into black holes and transform neutron stars into black hole matter, even if you read this sentence.
The team’s paper has been published on arXiv.