Black holes are usually imagined as giant cosmic monsters that form when massive stars die. But scientists believe another type of black hole may also exist—one that is incredibly tiny and may have formed shortly after the Big Bang. These objects are called primordial black holes (PBHs).
A new study has explored what would happen if one of these tiny black holes became trapped inside a star like our Sun. The results are surprising. According to the research, even an extremely small primordial black hole could slowly grow over time and eventually consume the entire star.
What Are Primordial Black Holes?
Primordial black holes are different from the black holes we normally hear about. They are not created by collapsing stars. Instead, scientists think they may have formed in the first moments after the Big Bang, when the Universe was extremely hot and dense.
Some of these black holes could be very small. In fact, the study examined primordial black holes with masses as low as one ten-quadrillionth of the Sun's mass. Despite being tiny, they still have incredibly strong gravity close to their surfaces.
If a primordial black hole were sitting at the center of a star, it would continuously pull in nearby gas and matter. Over time, this feeding process could make the black hole grow larger.
A Tiny Object With Extreme Effects
The black holes studied are unbelievably small. For example, a primordial black hole with a mass of about 10⁻¹⁶ times the Sun's mass would have a Schwarzschild radius of only about 10⁻¹¹ centimeters.
That is much smaller than an atom.
Even though the black hole is tiny, matter falling toward it experiences enormous gravitational forces. As gas gets closer and closer, it becomes compressed and heated to incredible temperatures.
The researchers found that temperatures near the black hole can reach around 100 billion degrees Kelvin. For comparison, the center of the Sun is only about 15 million degrees Kelvin.
At such extreme temperatures, the gas behaves very differently from what older theories predicted.
Studying How the Black Hole Feeds
To understand this process, scientists created detailed computer simulations.
They studied how gas from a Sun-like star falls toward a primordial black hole at the center. Unlike previous studies, they included realistic physics that describes how hot gas loses energy through radiation.
This allowed them to calculate two important things:
How fast the black hole grows.
How much energy escapes as radiation.
The results showed that the feeding process is much more complicated than scientists previously thought.
Instead of behaving the same way at all times, the black hole passes through different growth stages as it becomes larger.
Stage 1: The Hot Bondi Phase
The first stage occurs when the primordial black hole is extremely small.
In this phase, the gas falling toward the black hole becomes very hot, but it cannot cool efficiently. Because little energy escapes, the gas remains heated to around 100 billion degrees.
Scientists call this the Hot Bondi regime.
During this stage, the flow of gas is mainly controlled by gravity. The black hole steadily pulls in material from the surrounding star and slowly gains mass.
Although the growth is not yet dramatic, the conditions near the black hole are already extreme.
Stage 2: The Cooling Phase
As the black hole becomes slightly larger, a new effect starts to appear.
The hot gas begins losing energy through a process called bremsstrahlung radiation. This happens when fast-moving electrons interact with charged particles and release energy as radiation.
Because the gas can now cool more effectively, its behavior changes.
Cooler gas creates less pressure. With less pressure pushing outward, gravity can pull matter inward more easily.
As a result, the black hole begins feeding faster.
The researchers found that the gas flow gradually becomes more stable and uniform during this stage. The black hole also becomes more efficient at converting infalling matter into radiation.
This marks an important turning point in its growth.
Stage 3: The Photon-Trapping Phase
When the black hole grows beyond a certain size, another major change occurs.
The region around it becomes so dense that light can no longer escape easily. Photons, which are particles of light, become trapped inside the inflowing gas.
Scientists call this the photon-trapping regime.
Normally, radiation escaping from a black hole's surroundings can slow down accretion by pushing material away.
But when photons become trapped, this braking effect becomes much weaker.
Instead of escaping, much of the radiation gets dragged inward along with the gas.
This allows the black hole to continue growing rapidly.
Cooling Actually Helps Growth
One of the most surprising discoveries of the study is that cooling helps the black hole grow faster.
At first this may sound strange. Many people would expect cooling to reduce activity.
However, when gas cools, its pressure decreases. Lower pressure means there is less resistance against gravity.
Because of this, the black hole can pull in material more efficiently.
The researchers found that cooling increases the accretion rate by about two to seven times compared with older models.
This means primordial black holes hidden inside stars could gain mass much faster than scientists previously believed.
Less Radiation Than Expected
Previous studies often assumed that these black holes would release large amounts of radiation while feeding.
The new simulations tell a different story.
The researchers found that the radiative efficiency is about ten times lower than many earlier estimates.
In simple terms, the black hole produces less outward energy than expected.
This is important because strong radiation can slow growth by pushing away incoming gas.
If less radiation escapes, there is less opposition to the inflowing matter.
As a result, the black hole can continue feeding more efficiently and grow faster.
Could a Tiny Black Hole Destroy a Star?
The most dramatic result of the study involves the long-term fate of a star hosting a primordial black hole.
Scientists calculated the minimum starting mass needed for a primordial black hole to eventually consume a Sun-like star.
They found that a black hole with an initial mass of only about 10⁻¹⁶ times the Sun's mass could potentially destroy the entire star within the age of the Universe.
This threshold is much smaller than previous estimates suggested.
In other words, even a microscopic primordial black hole could have a huge impact if it remained trapped inside a star for billions of years.
The process would be extremely slow at first. For most of the star's life, there would be little sign that anything unusual was happening.
But over time, the black hole would continue growing until it eventually consumed a significant portion of the star.
Why This Discovery Matters
Primordial black holes are still hypothetical. Scientists have not yet confirmed that they exist.
However, they remain one of the most interesting possibilities in modern astrophysics. Some theories even suggest that primordial black holes could make up part of the mysterious dark matter that fills the Universe.
This new study provides one of the most detailed looks yet at how primordial black holes would behave inside stars.
The results show that tiny black holes may grow faster, shine less brightly, and survive more easily than previous models predicted.
If primordial black holes are real, they could quietly influence the lives of stars throughout the cosmos.
A black hole smaller than an atom may seem insignificant, but this research reveals that given enough time, even the tiniest black hole could become a powerful force capable of consuming an entire star from the inside out.
Reference: Matteo Cantiello, Ore Gottlieb, Cameron Norton, Matthew Kleban, Ken Van Tilburg, "Accretion of Primordial Black Holes in Stellar Interiors", Arxiv, 2026. https://arxiv.org/abs/2606.02726
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