Some stellar explosions could be triggered by black holes formed at the beginning of the Universe. This hypothesis remains theoretical, but a new study shows that it could explain certain chemical characteristics observed in the Milky Way.
The objects in question are primordial black holes. Unlike black holes resulting from the collapse of a star, they are extremely small and would have appeared when the Universe was still very young. Their existence has not been confirmed, but they are among the possible candidates to explain dark matter.
Tiny, primordial black holes would have formed at the very beginning of the Universe
According to the studied scenario, a primordial black hole would pass through a white dwarf. This compact star corresponds to the final stage of a low-mass star, after the disappearance of its outer layers. Despite its small size, it contains an amount of matter comparable to that of the Sun.
As it moves through the white dwarf, the black hole would exert a very intense gravitational attraction on the surrounding matter. This passage would heat a zone around its trajectory. If the temperature became high enough, an uncontrolled nuclear reaction could start.
The resulting explosion would then be a Type Ia supernova. These events are notably used to measure distances in the Universe, because their intrinsic brightness can be estimated. Understanding their origins is therefore important for reconstructing the history of cosmic expansion.
The researchers compared their simulations to several supernova remnants, as well as to explosions observed in nearby galaxies. They also studied the chemical elements present in the stars of the Milky Way, notably different isotopes of nickel and manganese.
The model indicates that a small fraction of Type Ia supernovae could originate from this mechanism. Even very rare, this contribution would help explain a trend in the chemical composition of stars in our galaxy.
No primordial black hole has been directly observed. The interest of this study therefore comes from the indirect traces they could leave in stellar explosions and the composition of matter. The researchers still need to test this scenario on more supernovae and stellar populations.