Tiny black holes may be secretly exploding stars across the Milky Way
An international research team has found that primordial black holes may trigger white dwarf stars to explode as Type Ia supernovae. These unusual explosions could also help explain a chemical abundance pattern observed among stars in the Milky Way, according to a recent study published in The Astrophysical Journal.
Primordial black holes (PBH) are hypothetical remnants of the universe's earliest moments. Scientists think they may have formed during cosmic inflation, when rapid expansion amplified small fluctuations in the distribution of matter.
These black holes have been proposed as possible candidates for dark matter, the invisible material thought to account for about 90% of all matter in the Universe by mass. Although dark matter cannot be seen directly, its gravitational effects can be detected throughout galaxies and across the wider cosmos.
Primordial black holes could travel through stars as they move across the universe. Earlier research suggested that if one passed through a white dwarf, its gravity could create powerful tidal forces inside the star. Those forces might destabilize the white dwarf and cause it to explode as a Type Ia supernova (SNe Ia).
A white dwarf is the dense stellar remnant left behind after a low-mass star runs out of fuel. Type Ia supernovae are extremely bright explosions that are generally believed to occur when a white dwarf becomes unstable and undergoes a runaway thermonuclear reaction.
Testing a New Path to Type Ia Supernovae
The research was led by Shing-Chi Leung, an assistant professor at SUNY Polytechnic Institute and a visiting associate scientist at The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU). The team also included Kavli IPMU Visiting Senior Scientist Ken'ichi Nomoto and Kavli IPMU Senior Fellow Alexander Kusenko.
The scientists investigated the motion, brightness, and chemical properties of supernovae produced through this proposed PBH-triggered explosion channel.
In an earlier paper published in 2025, the team showed that PBH-triggered explosions could produce SNe Ia with properties that closely resemble those generated by standard Type Ia supernova models.
Comparing Models With Real Supernovae
For the new study, the researchers compared their models with several well known supernova remnants (Tycho, Kepler, 3C 397), nearby supernovae (e.g., SN 2011fe, SN 2012cg) and the chemical abundances of Milky Way stars.
Their results showed that PBH-triggered SNe Ia could reproduce several characteristics observed in these supernovae and their remnants.
The researchers examined radioactive isotopes such as Ni-56, Ni-57, and stable elements such as Mn and Ni. These chemical signatures allowed them to estimate the masses and metallicities of the stars that produced the explosions.
Metallicity (the amount of metal when the star is formed, which probes when the star is born in the cosmic age) can provide clues about when a star formed and the chemical conditions that existed at that point in the history of the universe. In astronomy, metals are elements heavier than hydrogen and helium.
Primordial Black Holes May Shape Galactic Chemistry
The team also used supernova models to explore how this explosion mechanism could contribute to galactic chemical enrichment. Supernovae release newly formed elements into space, where those materials can later become part of new stars and planets.
The analysis indicated that a non-zero fraction of PBH-triggered SN Ia may be needed to explain the chemical abundance trend observed in stars across the Milky Way. This suggests that primordial black holes may have influenced the chemical evolution of our galaxy through the stellar explosions they triggered.
"Our work suggests that some supernova that we observe in the sky could be a result of the PBHs. Therefore, even though we cannot directly observe these evasive entities, they leave many interesting clues in nature for us to probe their properties," Leung said.
The researchers plan to broaden their investigation by studying how PBH-triggered explosions might affect the overall population of conventional supernovae and the combined rates of these brief but powerful cosmic events.
Reporting from ScienceDaily contributed to this story.
