Could Primordial Black Holes Be Hiding in Plain Sight?

An artistic take on primordial black holes. Credit: NASA’s Goddard Space Flight Center

Are Primordial Black Holes (PBHs) real? They could have formed during the unusual physics that dominated the Universe shortly after the Big Bang. The idea dates back to the 1960s, but so far, the lack of evidence makes them purely hypothetical.

If they do exist, a new paper suggests they may be hiding in places so unlikely that nobody ever thought to look there.

Black holes form when massive stars reach the end of their lives and suffer gravitational collapse. However, PBHs didn’t involve stars. Physicists hypothesize that PBHs formed in the early Universe from extremely dense pockets of sub-atomic matter that collapsed directly into black holes. They could comprise part or all of what we call dark matter.

New research titled "Searching for small primordial black holes in planets, asteroids and here on Earth", co-authored by De-Chang Dai and Dejan Stojkovic, suggests that we are not looking in the right places for evidence of PBHs. This study, published in Physics of the Dark Universe, posits that the evidence for PBHs could be found in objects as large as hollowed-out planetoids or asteroids and as small as rocks here on Earth.

Hollowing Out Asteroids

"Small primordial black holes could be captured by rocky planets or asteroids and consume their liquid cores from inside, leaving hollow structures," state the authors. "Alternatively, a fast black hole can leave a narrow tunnel in a solid object while passing through it, possibly providing clues to their existence right here on Earth."

The authors point to other research suggesting that PBH masses between ¹⁰₁₆ and ¹⁰₁₀ solar masses might be candidates for dark matter. These PBHs could be trapped in stars or other celestial bodies upon formation and might slowly consume gas inside them.

Extending the idea to planets and asteroids, Dai and Stojkovic state that PBHs could have been captured by these objects either during their formation or after, potentially hollowing them out as they consumed their liquid cores. The resultant structures might be detectable by examining the density of asteroids and other bodies.

Hollow Objects and Micro-Tunnels

"If the object has a liquid central core," explains Stojkovic, "then a captured PBH can absorb the liquid core, whose density is higher than the outer solid layer." This could leave a detectable signal in the form of hollowness in celestial bodies. According to Stojkovic, "If the object’s density is too low for its size, that’s a good indication it’s hollow." Astronomers might be able to study an object’s orbit with a telescope to reveal hollowness.

If the asteroid or other celestial body suffers an impact, the PBH could escape, leaving behind only a hollow shell, which could be detected. Detection methods would not necessarily require expensive equipment or advanced technology.

Fast-Moving PBHs

Another clue proposed in the research is that fast-moving PBHs might leave microscopic tunnels in solid materials. The authors state, "Since the cross-section of a small PHB is very small, a fast enough PBH will most likely create a straight tunnel after passing through the asteroid." A straight tunnel or micro-tunnel could serve as evidence of PBH interaction within asteroids.

The search for PBHs differs from traditional search methods which rely on space telescopes or gravitational wave observatories. "What’s different about this hypothesized method is that detection is potentially much cheaper and easier," state the authors.

PBHs present intriguing questions within the context of dark matter research. “The chances of finding these signatures are small,” says Stojkovic, “but searching for them would not require much resources and the potential payoff, the first evidence of a primordial black hole, would be immense.” This emphasizes the necessity of thinking "outside of the box" when it comes to detecting these elusive cosmic features.

Conclusion

Could primordial black holes exist in places that we have overlooked? Given the rich and fascinating nature of the universe, the possibility remains that these anomalies may hold the key to unraveling some of the darkest mysteries of cosmology. Future studies focusing on micro-tunnels in solid materials on Earth and asteroids may shed new light on the existence of primordial black holes.

For More Information

For further reading on primordial black holes and their potential implications for our understanding of dark matter, consider the following resources:

• Searching for small primordial black holes in planets, asteroids and here on Earth
• Further research on PBHs and their properties

The ongoing exploration of primordial black holes draws upon a vast array of scientific disciplines and points to the necessity for diverse methodologies in comprehending our universe's complexities.

References:

Universe Today. (2024). Could Primordial Black Holes Be Hiding in Plain Sight?