Researchers have studied what would happen if a hypothetical asteroid-mass black hole intersected a white dwarf. The simulations reproduce some light curves and chemical signatures measured in supernovae, but do not prove that primordial black holes exist.
Is some of itsupernovae Type Ia stars begin when a tiny dark object crosses a white dwarf? New theoretical research suggestsprimordial black holes Those with a mass similar to that of asteroids may ignite the thermonuclear explosions and leave behind signatures that can, at least in principle, be measured.
It is important to make a caveat at the outset: primordial black holes have not yet been discovered. The study does not report the observation of such a black hole, nor does it prove that it caused a particular supernova. The researchers tested whether such a hypothetical scenario could reproduce the properties of supernovae and supernova remnants that have actually been observed.
The research, led by Shing-Chi Leung of the State University of New York Polytechnic Institute and the Quali Institute for the Physics and Mathematics of the Universe at the University of Tokyo, was published in June 2026 in the journal The Astrophysical Journal. The scientific article
Black holes that were not formed from stars
The black holes that astronomers are familiar with are usually formed by the collapse of massive stars or the merger of compact objects. Primordial black holes are a different idea: They are thought to have formed shortly after the Big Bang, when extremely dense regions in the young universe collapsed under the influence of gravity.
The possible masses of such black holes span a wide range. The current study focuses on the so-called "asteroid mass window" — between (4\times10^{-17}) and (4\times10^{-12}) times the mass of the Sun. Despite their relatively large mass, such a black hole would be too small to emit light or be directly visible in telescopes.
Primordial black holes have been proposed as one of the candidates for composing some of the dark matter, which constitutes about 85% of all matter in the universe. However, there are strict observational constraints on their abundance over many mass ranges, and there is currently no consistent evidence that they exist.
A short passage that could ignite a star
A white dwarf is the dense core that remains after a low- or intermediate-mass star completes its development. White dwarfs Composed primarily of carbon and oxygen, they may, under certain conditions, undergo uncontrolled thermonuclear combustion and explode asA type Ia supernova.
In conventional scenarios, the explosion is associated with a binary system: the white dwarf either accreting material from a companion star or merging with another white dwarf. However, the precise pathways leading to all Type Ia supernovae are not yet fully understood, and it is possible that more than one mechanism can cause them.
The new scenario suggests another possibility. If a primordial black hole were to intersect a white dwarf, its gravity would exert strong tidal forces on the material near its orbit. These forces would heat a narrow region inside the star. When the temperature reaches about half a billion Kelvin, the rate of carbon burning could overwhelm the rate of neutrino cooling.
If the heated region is large enough, a local thermonuclear escape will begin. The combustion wave will spread throughout the white dwarf and may lead to its complete explosion. The black hole itself is expected to continue on its orbit, making it very difficult to detect after the event.
Comparison to real supernovae
In a previous study, published in 2025, the same group of researchers demonstrated the ignition of the white dwarf and the evolution of the explosion. The simulations produced supernovae with light curves similar to those of regular Type Ia supernovae and even matched the Phillips ratio—the relationship between the peak intensity of a Type Ia supernova and the rate of its brightness decay.
In the new study, the team extended the simulations to white dwarfs with different masses and metallicities. Metallicity is the proportion of elements heavier than hydrogen and helium in the material from which the star formed, and it affects the types of isotopes produced in the explosion.
The researchers compared the models' results to the relationships between Nickel-56 for nickel-57 measured in nearby supernovae, including SN 2011fe, SN 2012cg, SN 2013aa, and SN 2014J. Several of the models fit the measured ratios, particularly for supernovae thought to originate from white dwarfs with masses below the Chandrasekhar limit.
A comparison was also made between the quantities ofmanganeseThe models predicted the nickel and iron content of the Kepler, Tycho and 3C 397 supernova remnants. The models came close to the measurements of the Kepler and 3C 397 remnants under certain conditions, but failed to explain the Tycho remnant. According to the researchers, Tycho fits better with conventional models of Type Ia supernovae. The open version of the article on arXiv
A model-observation fit does not prove that the event was caused by a primordial black hole. Other explosion trajectories can produce similar light curves and chemical compositions, so more unique signatures are needed to distinguish between the possibilities.
A fingerprint in the chemistry of the Milky Way
Supernovae enrich their surroundings with the elements created during the explosion. New generations of stars are formed from the enriched gas, so the elemental ratios in the Milky Way's stars preserve information about the supernova population that preceded them.
The researchers incorporated the simulations into a model of the chemical evolution of the galaxy and compared the results to measurements of silicon, sulfur, argon, calcium, manganese, and nickel in stars. Some of the best fits require a non-zero rate of supernovae from the orbit that ignite primordial black holes, especially in the early universe.
However, this conclusion also depends on the model's assumptions: the frequency of primordial black holes, the history of star formation, the other types of supernovae, and the amounts of elements each produces. Therefore, it is not possible to infer from the fit what proportion of supernovae are actually caused in this way.
More precise measurements of supernova remnants, including those using the XRISM X-ray Observatory, may narrow the range of possibilities. If a chemical or observational combination is found in the future that is difficult to explain by conventional scenarios, it will be possible to examine more seriously the involvement of primordial black holes. Kavli Institute IPMU Announcement
Questions and Answers
What is a primordial black hole? A hypothetical object that could have formed from the collapse of dense regions in the early universe, rather than from the collapse of a star. So far, no direct evidence has been discovered for the existence of such black holes.
How can a small black hole ignite a white dwarf? As it passes through the star, its gravity may heat the material along its path. If the heating ignites uncontrolled carbon combustion, it could spread and lead to a supernova.
Was one of the supernovae examined definitely caused by a primordial black hole? No. Some of the models fit measurements from certain supernovae, but other explosion scenarios could explain similar data.
How can the hypothesis be tested? Through precise measurements of light curves, isotope ratios, and the composition of supernova remnants, and by searching for differences that are not well explained by accepted models.
More on the subject on the science website
- Is dark matter made of black holes?
- Physicists: Within a decade, we may see a primordial black hole exploding
- Double explosion: For the first time, remnants of a star that exploded twice have been observed
- Hubble captures a Type Ia supernova 650 million light-years away
- SN 2011fe — Bright supernova in the galaxy M101
For the scientific article: Opening the scientific article
