It’s been a fantastic week for Stephen Hawking’s black hole theories. Yesterday, LIGO confirmed the famed physicist’s prediction about black hole mergers. Now, another team believes they’ve found a way to observe primordial black holes—cosmic behemoths that emerged not from the ashes of dying stars but from the chaos of the early universe.
In a paper published September 9 in Physical Review Letters, a team of physicists make the bold prediction that, within the next decade, we will be able to witness the explosive death of a black hole—and specifically, a primordial black hole. Studying the radiation emitted from this event, they theorize, would offer an unprecedented look into the dynamics of the early universe.
“We’re not claiming that it’s absolutely going to happen this decade,” Michael Baker, one of the study’s co-authors, said in a press release. “But there could be a 90% chance that it does. Since we already have the technology to observe these explosions, we should be ready.”
What happens when black holes die
Black holes are among the most powerful entities in our universe, but as with all things, black holes eventually “die,” explosively. Hawking predicted that in the lead up to this cataclysmic end, black holes emit a very slow stream of photons and subatomic particles—a phenomenon later dubbed as Hawking radiation.
In theory, current gamma-ray observatories should be able to spot Hawking radiation. The issue is that black holes live for a very long time, and scientists believe that such explosions occur and enter our detection range maybe once every 100,000 years.
A dark version of events
Baker and his colleagues think we may not have so long to wait. They reworked a long-held assumption that black holes are electrically neutral. Since primordial black holes and their (comparatively) younger peers have different origin stories, they wondered if primordial black holes could also have different electrical characteristics.
After some theoretical exploration, the team settled on what they call the “dark-QED toy model.” In this scenario, primordial black holes have a small, “dark” charge powered by “dark electrons,” which are a very heavy, hypothetical version of the electron.
“It sounds quite esoteric, but within that field it’s quite a common thing to do,” Baker told The Boston Globe. They found that a slightly charged primordial black hole would, theoretically, explode pretty early in the universe’s history. The extra charge would suppress the Hawking radiation, which would extend the lifespan of those primordial black holes already thought to have exploded by now.
“Because the only black holes that can explode today or in the near future are these [primordial black holes], we know that if we see Hawking radiation, we are seeing an exploding [primordial black hole],” study co-author Joaquim Iguaz Juan said in a statement.
If their predictions withstand further scrutiny and eventually prove correct, scientists could glean “a definitive record of every particle that makes up everything in the universe,” he said, adding that such a discovery would “completely revolutionize physics and help us rewrite the history of the universe.”
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