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Scientists may have found a new way to detect some of the universe's most mysterious objects, primordial black holes (PBHs), using Hawking radiation. This groundbreaking approach relies upon watching for their radiation signatures as they pass through the solar system. This technique could finally help us to solve one of cosmology's biggest puzzles: what makes up the invisible dark matter that comprises 85% of all matter in the universe.

The nature of dark matter still eludes us. We know it exists because we can see its gravitational effects on galaxies and other cosmic structures, but we've never established what it actually is. Among the leading candidates are PBHs, ancient black holes that formed in the universe's earliest moments from extremely dense pockets of matter created shortly after the Big Bang.

The key to detecting these ancient objects, a new paper proposes, lies in Hawking radiation, a phenomenon where all black holes emit radiation inversely proportional to their mass. Smaller black holes radiate more intensely while large black holes radiate less. Previous attempts to detect them relied on studying cosmic background radiation, but this new idea suggests we might be able to detect individual black holes as they zip through our solar system.

The beauty of this method lies in its precision. Instead of extracting faint signals from the cosmic background, scientists would look for distinctive time-dependent spikes in positron detection as a PBH passes near Earth. Positrons are the focus of this study even though Hawking radiation is actually a broad spectrum that includes neutrinos, other fundamental particles, and of course positrons. The positron was selected because this component of Hawking radiation is easier to detect with the Alpha Magnetic Spectrometer (AMS) mounted upon the International Space Station.

, which was led by Alexandra P. Klipfel and is posted to the arXiv preprint server, involves calculating how often these ancient black holes might transit through the inner solar system and simulating the radiation signatures they would produce. The results are promising: Simulations yield about one detectable PBH transit per year.

This represents a dramatic improvement over current detection methods. Instead of relying on complex models of cosmic ray propagation and galactic dark matter distribution, all of which introduce uncertainties, this approach would provide direct, local measurements with precise timing information.

What makes this research exciting is that it could finally detect PBHs that scientists haven't been able to find before. The researchers show that by measuring positrons every day (using the same quality of data that AMS already collects), they could spot the specific types of ancient black holes that might make up most of dark matter.

The technique could also be extended beyond positrons. The researchers suggest that looking for gamma-ray and X-ray emissions from Hawking radiation could probe even further into the asteroid-mass window (PBH masses ranging from 10¹⁷ grams, about the mass of a small asteroid, to 10²³ grams, comparable to the mass of Ceres) potentially covering the full range where PBHs could constitute all of dark matter.

This approach represents a significant shift in dark matter detection from passive observation to active hunting for individual objects in our very own neighborhood. If successful, it wouldn't just detect dark matter; it would provide detailed information about PBH mass distribution and abundance.

As detection capabilities improve and new space-based observatories come online, this technique could finally answer whether the invisible scaffolding of our universe consists of ancient, asteroid-sized black holes drifting through space, occasionally betraying their presence through the faint glow of Hawking radiation.