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. But in one Kuiper Belt region, these co-orbiting objects are roughly equal in mass, and a small number are also widely separated. This causes a great deal of instability, said lead author Hunter Campbell, a graduate of the University of Oklahoma, where the research was conducted.
Planetary Science Institute Senior Scientist Nathan Kaib was a co-author on this paper and helped conceive of the project and assisted with simulation software development.
The existence, formation, history and evolution of these co-orbiting, widely separated objects have been the subject of past research. Many have hypothesized that collisions with smaller bodies disrupt the orbits of the paired bodies and cause one of them to migrate further away, but the team demonstrated a different hypothesis.
Gravitational interactions are an equal, if not stronger, factor in the long-term stability of these objects, they found. It’s more likely that a large Kuiper Belt body would pass near two co-orbiting objects and its gravity would pull one object away from the other.
Before this research, it was assumed that these widely separated bodies formed as they are now and simply survived the Solar System’s 4 billion years of existence. This work has shown that the co-orbiting systems could have started with much tighter orbits and widened thanks to the gravitational pull of large passing bodies.
“The fact that these ultra-wide binary systems could’ve been formed relatively recently is the most surprising to me, since it’s usually been assumed that they are about as old as the Solar System,” Kaib said.
These simulations are the first step in making potentially important future discoveries.
“Next, it would be great to see if impacts with small Kuiper Belt objects change, or accelerate, the binary widening process. In this paper, we only simulate close encounters where gravitational interactions widen the binaries, but do not simulate physical collisions between bodies.”
Other future research could help scientists understand how the Kuiper Belt migrated to its current position, for example, and how that migration impacted how the outer planets of Jupiter, Saturn, Uranus and Neptune moved throughout history.
The PSI portion of this work was funded by a NASA Emerging Worlds grant (80NSSC23K0771).
This cover story was adapted from a press release by the University of Oklahoma.