Parasitic black holes could eat stars from the inside: ScienceAlert

There could be an unusual dark matter filter lurking inside stars, slowly eating them from the inside out.

A new paper led by astrophysicist Earl Bellinger of the Max Planck Institute for Astrophysics and Yale University suggests that very small black holes that formed at the dawn of time could have coalesced into Sun-like stars, and remained at their core ever since. , gradually devouring material and turning it into more black holes.

This is all very hypothetical, of course. But the study examines the effect of such intrusion on these stars, and how we can identify them in the universe, if they occur.

“We found that such objects can be surprisingly long-lived, with lighter black holes having no effect on star evolution, while larger black holes consume the star over time to produce a host of observable consequences.” The researchers write in their paper.

“The unique internal structures of stars that harbor black holes may make it possible for astroseismology to detect them, if they exist.”

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The universe is full of black holes of different sizes. We’ve seen black holes with stellar mass domains, which likely formed from the core collapse of a massive star at the end of its life, and its mergers. There are enormous monsters, millions to billions of times the mass of the Sun, lurking at the heart of every galaxy. There are black holes with masses in between, elusive but appearing in increasing numbers.

What we haven’t found are actually very small black holes, ones with masses similar to those of planets, moons, or asteroids. These objects do not have enough mass and thus enough gravity to collapse into something dense like a black hole.

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But there is a way tiny black holes could form, in theory.

According to a theory developed by Stephen Hawking in the 1970s and expanded by other scientists since then, mini black holes could have formed in the first second or so after the Big Bang, when matter in the universe was still hot and dense enough for specks to form. Excess density can collapse into inevitable patches of spacetime.

Where these “primordial” black holes went – if they existed at all – remains a mystery, but they would be a neat explanation for the extra gravity in the universe that we attribute to dark matter.

Some scientists think they could end up inside neutron stars, sitting in the cores and munching like some alien cosmic tapeworm.

Bellinger and his colleagues wanted to investigate the possibility Parasitic black hole, not in a dead stellar remnant like a neutron star, but in a living star embedded in the main sequence like the Sun. Hawking himself suggested this The Sun could be home to a primordial black hole. Other scientists conducted theoretical analyzes and determined that A The primordial black hole will devour a star from the inside.

For their analysis, Bellinger and his team calculated what would happen to a star between 0.8 and 100 solar masses forming around a primordial black hole with the mass of a star. They also performed the first fully numerical evolutionary simulations of Sun-like stars with primordial black holes lurking in their cores.

The researchers found that the smallest black holes would have difficulty growing. It would take billions of years for the black hole to consume the star.

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But a black hole with the mass of a dwarf planet would be much more sinister. It will begin to consume the core of a sun-like star, with material swirling around it to form a disk that begins to produce massive amounts of light and heat.

Within a billion years, nuclear fusion will no longer power the star; Instead, this star will be powered by the accretion disk orbiting the black hole. Ironically, all of the star’s light will be produced by the black hole. Researchers have called this hypothetical type of star a Hawking star.

An ordinary red giant star named R Sculptoris. (worst. Fuji/Digital Sky Survey 2)

Hawking’s star behaves somewhat similarly to a regular star, with a few key differences. Its outer layers will inflate to form a red giant, just as the Sun is expected to do as nuclear fusion begins to die down at the end of its life. But its temperature will be cooler than we might expect from such a star. Interestingly, we have already found unusually cool red giant stars in the Milky Way. They are called red radicals.

Researchers say we can study these stars to look for signatures of the black hole’s engine. Black hole accretion is expected to produce different acoustic patterns inside the star than merger, which can be detected with subtle changes in brightness on the star’s surface. What the brightness changes look like is unknown at this point; The researchers aim to address this question in a future paper.

“This represents an opportunity to detect such objects, or set limits on their number and capture rate.” The researchers write.

“Implications for stars at more advanced evolutionary stages, numerical results for stars with different masses and metallicities, and investigations of stellar populations will also be explored in future work.”

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The research was published in Astrophysical Journal.

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