Dark Charge Could Make Exploding Black Holes More Common
Black holes are thought to evaporate by emitting Hawking radiation—photons and assorted subatomic particles—from just beyond their event horizons. The characteristic temperature of this emission, and therefore the evaporation rate, is inversely proportional to the black hole’s mass. When the mass dwindles to nothing, an explosive finale ensues. The process is so slow that lightweight black holes created in the early Universe could be entering their terminal phases only now. Current gamma-ray observatories should be able to spot one of these exploding primordial black holes if it’s within about 0.3 light-years. But because of the black holes’ presumed scarcity, detectable events should occur only once every hundred thousand years or so. Michael Baker and colleagues at the University of Massachusetts Amherst have proposed that some beyond-standard-model theories, if correct, could spawn a much larger population of these black holes [1]. The proposal implies that there’s up to a 90% chance of observing an exploding black hole in the next ten years.
For every black hole that explodes, large numbers of pre-explosion black holes must be radiating more faintly, adding to the gamma-ray background. The number of explosions that we should expect to see depends on the size of the primordial black hole population, which cannot exceed the level inferred from the background. Baker and colleagues calculated the existence of so-called dark-sector particles analogous to conventional photons and electrons could mean that more black holes can fit within that observational constraint. Using a simple model of dark quantum electrodynamics, they hypothesized that black holes acquire a dark electric charge soon after forming. This charge suppresses their Hawking emission, minimizing their contribution to the gamma-ray background. It also extends the lifetimes of small black holes that would otherwise have exploded by now.
–Marric Stephens
Marric Stephens is a Corresponding Editor for Physics Magazine based in Bristol, UK.
References
- M. J. Baker et al., “Could we observe an exploding black hole in the near future?” Phys. Rev. Lett. 135, 111002 (2025).