Black holes are regions in spacetime with such strong gravitational fields that nothing can escape their boundaries, not even light. As a result, most of these massive objects invisibly drift through space, making it difficult to resolve the many open questions about their mind-bending properties.

Now, scientists have suggested there may be a way to confirm a key mystery about black holes—whether they produce vortex structures—by searching for specific signatures in space. These vortexes would be structurally similar to the swirling maelstroms of tornadoes and whirlpools, but they would arise in multiple places on black holes instead. 

In addition to shedding light on black holes, these clues could potentially open “an observational window to various hidden sectors” of the universe, including the nature of dark matter, according to a recent study published in Physical Review Letters.

While popular depictions of black holes often make them look like giant space vortexes, the presence of vorticity in these entities is a matter of debate. Researchers led by Gia Dvali, director at the Max Planck Institute for Physics in Germany, have presented new theoretical evidence that rapidly spinning black holes “naturally support a vortex structure” and that black hole vorticity could have “macroscopically observable consequences,” reports the study.

“The microscopic structure of black holes remains to be understood,” Dvali and his colleagues said in the study. “One of the main obstacles is the lack of experimental probes of black hole quantum properties. In this light, it is very important to identify and explore those microscopic theories that lead to macroscopically observable phenomena.” 

“We shall create awareness about one such phenomenon: vorticity,” the team added. “We believe that…the vorticity property in black holes can be understood without entering into the technicalities of quantum gravitational computations.”

The new research was partially inspired by experimental studies of Bose–Einstein condensates, an ultracold state of matter with bizarre quantum properties that are useful for modeling black hole behaviors. Many laboratory tests have revealed vortex formation in these condensates, which suggests that the structures may also arise in black holes with extremely fast spins, according to Dvali’s team.

The presence of vorticity could explain why rapidly rotating black holes don’t seem to produce Hawking radiation, a type of thermal glow emitted by some of these objects. The structures could also lead to extraordinary breakthroughs beyond black holes, including the opportunity to open a “portal into the sector of dark matter,” the study’s authors wrote. 

This figurative portal might lurk in extremely luminous objects called active galactic nuclei, which are powered by supermassive black holes that sit at the center of large galaxies. These nuclei shoot out huge jets of plasma that travel close to light speed and can extend across a million light years. 

Dvali and his colleagues note that these energetic jets might emit magnetic signatures of vorticity in their light, which could be captured and deciphered in telescope images. The jets are also thought to interact with dark matter, an unidentified substance that accounts for most mass in the universe. As a result, future observations of jets, and the possible signatures of vortexes within them, could inform the major scientific quest to understand dark matter.

"We have just recently established the field of black hole vorticity," said Florian Kühnel, a cosmologist at Ludwig Maximilian University of Munich who co-authored the study, in a statement. 

"There is a wealth of important and exciting questions to address that “might open the door to these new and exciting quantum aspects of space-time," he concluded.