The impression of the artist placing a small black hole in the center of the sun in a thought experiment. **wikimedia/creative commons。
In a hypothetical scenario, newly formed stars could capture small primordial black holes. An international team led by researchers at the Max Planck Institute for Astrophysics has now simulated the evolution of these so-called "Hodging stars" and found that they can have surprisingly long lifespans, similar in many ways to normal stars. The findings were published in the Journal of Astrophysics.
Asterachemiology can help identify these stars, which can test the existence of primordial black holes and their role as components of dark matter.
Let's do a scientific exercise: if we assume that a large number of very small black holes formed after the big ones (the so-called primordial black holes), some of them may have been acquired during the formation of new stars. How will this affect the star over its lifetime?
Scientists sometimes ask crazy questions just to learn more," said Selma de Mink, director of the star system at the Max Planck Institute for Astrophysics (MPA). "We don't even know if this primordial black hole exists, but we can still do an interesting thought experiment.
Primordial black holes formed in the very early universe with a wide range of masses, from small asteroids to thousands of solar masses. They may constitute an important component of dark matter and are also the seeds of supermassive black holes at the centers of galaxies today.
With a very small probability, a newly formed star can capture a black hole with the mass of an asteroid or small moon and then occupy the center of the star. Such a star is called a "Hawking star" and is named after Stephen Hawking, who first proposed the idea in an article in the 1970s.
The Kippenhahn diagram shows the evolution of the interior of the Sun with and without ** BH. The figure on the left shows the mass distribution and indicates the area of energy generation and transmission. The diagram on the right shows the radial distribution and indicates the photosphere radius (black line) and the solar radius (horizontal dashed line). The top panel corresponds to a normal model of solar evolution that evolves through MS until the core hydrogen is depleted, and then burns the hydrogen shell as a red giant. The panel at the bottom shows a model consistent with the current sun, with a bh growing in its center. Nuclear fusion (red) provides most of the sunlight until the mass of BH is sufficient for the reaction to be extinguished. BH drives convection (hatches), mixing the innermost layer of the core and eventually mixing the entire star. Notice the difference in the y-axis scale between the panels. **Journal of Astrophysics (2023). doi： 10.3847/1538-4357/ad04de
This black hole at the center of Hodking will only grow slowly, because the influx of gases that feed the black hole is hindered by the outflow of luminosity. An international team of scientists has now simulated the evolution of such a star, with a black hole with a different initial mass and a different accretion model at the center of the star. Their astonishing result is that when the mass of the black hole is very small, the star is essentially indistinguishable from an ordinary star.
Stars with black holes in the center can live surprisingly long," said Earl Patrick Bellinger, an MPA postdoc and now assistant professor at Yale University, who led the study. "Our Sun may even have such a huge black hole in the center of Mercury that we don't notice.
The main difference between such a Hodking star and an ordinary star is its proximity to the core, which becomes convective due to accretion onto the black hole. It does not alter the properties of the star's surface and does not allow for the current detection. However, it can be detected by the relatively new field of seismology, where astronomers are using acoustic oscillations to probe the interior of stars.
Also in their later evolution, in the red giant phase, black holes may result in characteristic features. In upcoming projects (as in plato), these objects may be found. However, further simulations are needed to determine what it means to put a black hole into a star of various masses and metallic degrees.
If it is true that primordial black holes formed shortly after the Great **, then looking for Hawking's stars could be one way to find them.
Although the Sun is used as a type of movement, there is good reason to think that Hawking is common in globular clusters and ultra-faint dwarf galaxies," notes Professor Matt Kaplan of Illinois State University, a co-author of the study.
This means that Hawking stars could be a tool to test the existence of primordial black holes, as well as their possible role as dark matter.
More information: Earl PBellinger et al., Solar Evolution Model with Black Holes, Journal of Astrophysics (2023). doi： 10.3847/1538-4357/ad04de