In the dark, icy outskirts of our solar system—far beyond Neptune’s orbit—astronomers have discovered a cosmic oddball that appears to be locked in an unusual gravitational dance with the eighth planet.
The object, dubbed 2020 VN40, is the first ever confirmed trans-Neptunian object (TNO) found in a 10:1 mean motion resonance with Neptune. In simpler terms, it’s a celestial body that orbits the Sun beyond Neptune, and it completes exactly one orbit around the Sun for every ten that Neptune completes.
The discovery, detailed in a new paper published in The Planetary Science Journal by a team of astronomers from the Center for Astrophysics at Harvard & Smithsonian, confirms a long-suspected class of orbital resonances and reveals a never-before-seen behavior that could challenge existing models of orbital dynamics.
“This discovery confirms that this distant resonance is populated, as a single detection is likely to be indicative of a large population that is difficult to detect due to observational biases,” the authors write in the study.
2020 VN40 was found during the Large inclination Distant Objects (LiDO) survey, a project designed specifically to hunt for TNOs with orbits tilted well above or below the solar system’s plane. This survey, conducted using powerful telescopes atop Maunakea in Hawaii, aims to expand our knowledge of the outer solar system.
Aided by years of follow-up observations, the LiDO team meticulously tracked the object’s orbit, eventually confirming its unusual gravitational relationship with Neptune.
“This is a big step in understanding the outer solar system,” lead author and researcher from the Center for Astrophysics at Harvard & Smithsonian, Dr. Rosemary Pike, said in a press release. “It shows that even very distant regions influenced by Neptune can contain objects, and it gives us new clues about how the solar system evolved.”
2020 VN40: A New Type of Orbital Behavior
While resonances in the outer solar system are not uncommon—Pluto famously resides in a 3:2 resonance with Neptune—what makes 2020 VN40 so intriguing is the nature of its motion. Most resonant objects oscillate around one of three “libration islands,” which are specific angles relative to Neptune, typically 90°, 180°, or 270°. However, 2020 VN40 also displayed long periods of oscillation around 0°, a behavior that had never been conclusively observed before.
This new type of motion, described by the researchers as “libration around 0°,” or more dramatically as “eyehole libration,” occurs due to the object’s unusually high orbital inclination of 33.4 degrees. This steep tilt allows the object’s argument of pericenter—the angle where its orbit comes closest to the Sun—to drive an entirely different gravitational relationship with Neptune.
“The value of ωTNO affects the resonant evolution for large-i objects because it affects where in a TNO’s orbit it experiences its point of closest approach to Neptune,” the authors explain in the study.
The term “ωTNO” (pronounced “omega T-N-O”) is an angle that describes where along an object’s stretched-out, tilted orbit it gets closest to the Sun, and by extension, where it passes nearest to Neptune.
For distant objects like 2020 VN40, this angle plays a crucial role in how the object interacts with Neptune’s gravity over time. Depending on ωTNO’s value, the object might swing close to Neptune when it’s above or below the planet’s orbital plane, or in a spot where gravitational interactions are weaker.
These subtle shifts can dramatically alter the object’s orbital behavior, causing it to wobble in unusual ways, such as the surprising oscillations observed at 0° in this study. Essentially, ωTNO acts like a dial that adjusts the gravitational “tune” between the object and Neptune.
2020 VN40’s strange angle of approach allows it to be influenced by Neptune’s gravity in a way never predicted in standard orbital models. This behavior could help astronomers refine their classification and modeling of other distant, tilted objects in the solar system.
Temporary Stability and the Mystery of “Sticking”
Despite its rare status, 2020 VN40 is not expected to remain in this orbital configuration forever. The study’s simulations suggest that the object is what scientists call a “scattering sticking” TNO. This type of body temporarily gets caught in a resonance due to gravitational nudges from the giant planets, particularly Neptune. Over time, these objects tend to drift out of resonance and continue wandering the outer solar system.
Out of 201 test orbits run by the research team—including one for the nominal orbit and 200 additional “clones” representing small measurement uncertainties—only four remained resonant with Neptune for over 90% of a billion-year simulation.
Most eventually drifted away. Yet even temporary sticking can last hundreds of millions of years, making these objects valuable probes of solar system dynamics.
“Because of the large number of clones that scatter away from the resonance, and the low fraction of total time the particles spend in resonance, even if they do not actively scatter, we consider this object a scattering sticking TNO,” the authors write.
Why the Discovery of 2020 VN40 Matters
The presence of 2020 VN40 in the 10:1 resonance adds to a growing body of evidence suggesting that the outer solar system may be more dynamically rich and populated than previously thought.
Before this, researchers had already confirmed objects in 5:1 and 9:1 resonances, and even suspected candidates in 8:1 and 10:1 configurations. But this is the first time a 10:1 resonator has been confirmed with such precision.
Moreover, the novel libration mode could force a reevaluation of how scientists model orbital behavior in these distant regions. Traditional models rely on a relatively simple structure of resonance “islands.” But the presence of stable libration around 0° suggests that these frameworks might be too simplistic.
From improving our understanding of planetary migration in the early solar system to better modeling the orbital evolution of Kuiper Belt objects, discoveries like 2020 VN40 provide rare data points in a field where direct observation is often frustratingly limited.
“The toy model of three libration islands… was insufficient to describe and classify these objects and our classification system required many iterations to correctly identify all of the periods of resonance,” researchers noted, calling for a more flexible, data-driven approach as future discoveries roll in from upcoming observatories like the Vera C. Rubin Observatory.
More Oddballs to Come?
The LiDO survey itself identified over 140 trans-Neptunian objects with inclinations greater than 14 degrees—many of which are still being analyzed. Preliminary evidence already suggests similar 0° libration behavior may be present in other high-inclination resonators, including objects in 5:1 and 7:1 configurations.
As detection techniques improve and observational coverage expands, astronomers expect to make more such discoveries, challenging the current understanding of the solar system’s outskirts. And every new oddball, like 2020 VN40, offers a clue to the complex gravitational choreography that governs our cosmic neighborhood.
“This new motion is like finding a hidden rhythm in a song we thought we knew,” co-author and professor at the University of California, Santa Cruz, Dr. Ruth Murray-Clay said. “It could change how we think about the way distant objects move.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com