New research from the University of Massachusetts Amherst indicates a probability of up to 90% for a primordial black hole to explode in the coming decade – an event that could provide direct evidence of Hawking radiation and reveal the list of all the particles in the universe – known, hypothesized, and even those we didn't even know existed.
Physicists have long believed that black holes explode at the end of their lives, and that such explosions occur – at most – once every 100,000 years. But a new study published in the journal Physical Review Letters by physicists at the University of Massachusetts Amherst found that there is a greater than 90% probability that one of these explosions will be seen within the next decade, and if we are prepared, our existing fleet of telescopes – in space and on Earth – will be able to witness the event.
Such an explosion would be strong evidence for the existence of a theoretical type of black hole that has never been observed—a “primordial black hole”—that could have formed less than a second after the Big Bang 13.8 billion years ago. Moreover, the explosion would provide us with a definitive catalog of all the subatomic particles that exist: those we have observed, such as electrons, quarks, and Higgs bosons; those we have only assumed to exist, such as dark matter particles; and everything else that is completely unknown to science. This catalog could finally answer one of humanity’s oldest questions: Where did everything that exists come from?
We know black holes exist, and we understand their life cycle well: a large, old star runs out of fuel, collapses in a particularly powerful supernova, and leaves behind a region of space-time where gravity is so strong that nothing—not even light—can escape. Such black holes are very massive and actually stable.
The black hole of the kind predicted by Hawking
However, as physicist Stephen Hawking showed in 1970, it is possible that another type of black hole – a primordial black hole (PBH) – was formed not by the collapse of a star but by the conditions of the early universe, shortly after the Big Bang. Primordial black holes, like the black holes we know, are so dense that almost nothing can escape from them – which is why they are “black”. However, despite their density, PBHs may be much lighter than the black holes observed so far. Hawking also showed that black holes have a temperature, and in theory they can slowly emit particles via what is now known as “Hawking radiation” if they get hot enough.
Andrea Tam, co-author of the study and professor of physics at the University of Massachusetts Amherst: “The lighter a black hole is, the hotter it should be and emit more particles. As PBHs evaporate, they become lighter, and therefore hotter, and emit more radiation in an accelerated process until they explode. This is Hawking radiation that our telescopes can detect.”
Still, no one has ever directly observed PBH.
Joaquim Iguaz Juan, a postdoctoral researcher in physics at the University of Massachusetts Amherst: “We know how to observe this Hawking radiation. We can see it with our existing telescope array, and since the only black holes that can explode today or in the near future are PBHs, we know that if we detect Hawking radiation – we see a PBH exploding.”
While most physicists since Hawking's time have believed that the chances of seeing a PBH explode are extremely slim, Iguaz Juan points out: "Our job as physicists is to challenge accepted assumptions, ask better questions, and build more precise hypotheses."
The team's new hypothesis? Get ready to see the explosion now.
Aiden Simmons, a research co-author and graduate student in physics at the University of Massachusetts Amherst: "We believe there is a probability of up to 90% of observing a PBH exploding within the next 10 years."
As part of the study, the researchers examined a "dark QED game model." This is essentially a copy of the electric force we are familiar with, but includes a hypothetical, very heavy version of the electron, which the team calls the "dark electron."
The team reexamined long-held assumptions about the electrical charge of black holes. Ordinary black holes have no charge, and assumed that PBHs are also electrically neutral.
Michael Baker, co-author and professor of physics at the University of Massachusetts Amherst: "We propose a different hypothesis. We show that if a primordial black hole formed with a small dark electric charge, then the model predicts that it would stabilize temporarily before eventually exploding."
After weighing all known experimental data, the researchers found that we could observe a PBH explosion not once every 100 years as previously thought, but once every decade.
Baker Adds: "We're not saying it will definitely happen this decade, but there's probably a 90% chance it will. Since we already have the technology to watch for these explosions, we should be prepared."
Iguazú Juan Concludes: "This will be the first-ever direct recording of Hawking radiation and PBH. We will also get a definitive record of every particle that makes up the entire universe. This will revolutionize physics and help us rewrite the history of the universe."
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