Are Kuiper Belt Orbiting Objects Breaking Up?

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NORMAN, OKLA. – A study recently published in the journal Nature Astronomy upends conventional wisdom regarding the formation and stability of pairs of orbiting objects in the Kuiper Belt beyond the planet Neptune.

“Nearly a third of all objects in the Kuiper Belt orbit one another, similar to the way the Earth and Moon interact,” said Hunter Campbell, lead author and 2023 graduate of the University of Oklahoma, where the research was conducted. “However, in one region of the Kuiper Belt, this population of co-orbiting objects are roughly equal in mass. This would be like an Earth orbiting another Earth – which doesn’t normally happen in our solar system. Of these, a small number are really widely separated, which causes a great deal of instability.”

The existence, formation, history and evolution of these co-orbiting, widely separated objects have been the subject of past research. Many previous studies have hypothesized that collisions from meteorites and other foreign bodies disrupt the orbits of paired bodies and cause one of them to get knocked away. Using the OU Supercomputing Center for Education and Research, Campbell’s team, which also included former OU professor Nathan Kaib and OU graduate teaching assistant Kalee Anderson, was able to demonstrate a different hypothesis.

“We analyzed a variety of models in our simulation and have been able to demonstrate that gravitational interactions are an equal, if not stronger, factor in the long-term stability of these objects. So, instead of having a meteorite collision causing disruption, it’s more likely that a really large Kuiper Belt body would pass through the binary system and its gravity would pull one object away from the other,” he said.

Before this research, it was assumed that these widely separated bodies formed as they are now and simply survived the solar system’s four-billion-year history. Now, Campbell’s team has shown that the co-orbiting systems could have started with much tighter rotations and widened thanks to the gravitational pull of large passing bodies.

“The most widely separated binary ever observed, QW322, is very unstable. We believe it formed as a much tighter binary and gradually widened. Perhaps in the future, it will completely separate and will be replaced by another widening binary,” he said.

These simulations are the first step in making potentially important future discoveries.

“If we were to do more research, we could pin down a lot of things we don’t know – like how the Kuiper Belt migrated to its current position and how that migration impacted how the outer planets of Jupiter, Saturn, Uranus and Neptune moved throughout history. Simply put, this research opens up a lot of new possibilities.”