And you believed that rush hour was the worst thing ever? According to recent research, many “cosmic intersections” have “traffic lights” that have failed, making black hole collisions practically certain.

Supermassive black holes, vast voids that encircle everything within massive galaxies, are cosmic monsters that reside at the center of all large galaxies. This whirling motion affects stars and their systems, matter disks that the galactic behemoth eats, and, incredibly, even other black holes, albeit smaller stellar mass ones.

Additionally, it seems that this kind of behavior surrounding supermassive black holes can result in cosmic “traffic jams,” which may play a crucial role in slowing down the orbits of stellar-mass black holes. Furthermore, the impacted black holes may be compelled to collide, combine, and form a larger daughter black hole rather than whizzing around.

Then, this process is repeated because of the supermassive black hole responsible for the traffic congestion, which has a mass that is millions or perhaps billions of times greater than the sun. This leads to other black hole collisions, which eventually produce stellar-mass black holes with masses ranging from three to a few hundred solar masses.

Looking broader, all of this indicates that the surroundings of supermassive black holes are ideal for supporting the formation of smaller black holes.

An accretion disk is a disk of gas and dust that surrounds some supermassive black holes and eventually feeds the black hole. Supermassive black holes’ gravitational pull creates strong tidal forces in those accretion disks that light them up brilliantly, forming an area known as an Active Galactic Nucleus (AGN).

The researchers behind the new traffic-jam discoveries are from Monash University, where they examined the dynamics of both embedded black holes and accretion disks.

Stellar-mass black holes in these accretion disks may migrate through the disk as a result of their interactions with the surrounding gas. According to the team’s theory, this causes stellar-mass black holes to gather in areas they refer to as “migration traps.” Because of the traffic congestion, there is a higher chance of two star mass black holes coming into contact, crashing into one another, and merging in these areas than anyplace else in the nearby galaxy.

In fact, team leader and researcher at Monash University School of Physics and Astronomy Evgeni Grishin went one step further and compared these migration traps for stellar-mass black holes surrounding supermassive black holes to congested intersections in our planet without functioning traffic lights.

“We looked at how many and where we’d have these busy intersections,” said Grishin. “Thermal effects play a crucial role in this process, influencing the location and stability of migration traps. One implication is that we don’t see migration traps occurring in active galaxies with large luminosity.”

The team’s findings not only have significant ramifications for our comprehension of the processes involved in mergers of stellar-mass black holes, but they may also eventually contribute to the advancement of gravitational wave astronomy since these mergers cause a burst of minute ripples in spacetime.

“We’re thrilled with the results, and we now are one step closer to discovering where and how black holes merge in galactic nuclei,” Grishin said. Gravitational wave astronomy and the study of active galactic nuclei have very bright futures.

“Despite these significant findings, much about the physics of black holes and their surrounding environments remains unknown.”