July 15, 2025, TUCSON, Ariz. – Orbiting in the outskirts of the Solar System is a mysterious object moving in rhythm with Neptune, according to a new paper published in the Planetary Science Journal.
The object, dubbed 2020 VN40, is part of a class of minor planets known as trans-Neptunian objects and is the first confirmed body to orbit the Sun once for every ten Neptunian orbits. This rhythmic relationship is referred to as resonance.
“This discovery helps expand our picture of how the orbits of distant objects are influenced by Neptune. It is the most distant confirmed object in an orbital resonance with Neptune, and the observed distribution of resonant objects provides vital clues to how Neptune and the other giant planets rearranged themselves after their formation,” said paper co-author Kathryn Volk, a senior scientist at the Planetary Science Institute.
The object’s average distance is 140 times farther from the Sun than Earth, and its orbit is tilted at about 30 degrees from the Solar System’s plane. The discovery was made by the Large inclination Distant Objects survey, or LiDO for short, using the Canada–France–Hawaii Telescope. Follow-up observations were made with Gemini Observatory and Magellan Baade.
What makes 2020 VN40 novel is the unique way it syncs its orbit with Neptune.
Most objects in resonance with Neptune come closest to the Sun when Neptune is far away from them. This object, on the other hand, comes closest to the Sun when it is also near Neptune. But this is only the case if an observer were to look at the Solar System from above. In reality, the object’s orbit slopes in such a way that it is actually far below the plane of the Solar System when it is closest to the Sun and Neptune, creating only an illusion of proximity to the gas giant.
“The object’s high orbital inclination leads to a novel kind of resonant behavior,” Volk said.
“This behavior hasn’t been seen before because the majority of observed trans-Neptunian objects are found closer to the plane of the planets,” said Rosemary Pike, the study’s lead author from the Center for Astrophysics, Harvard and Smithsonian.
And this discovery is just the beginning, according to the team, which includes Samantha Lawler of the University of Regina, Ying-Tung Chen of the Institute of Astronomy and Astrophysics, Academia Sinica and Ruth Murray-Clay of the University of California, Santa Cruz.
“With the imminent start of Rubin Observatory’s Legacy Survey of Space and Time,” Volk said, “we expect many more such discoveries to open a new window into the Solar System’s past.”
SCIENCE CONTACT
Kathryn Volk
Senior Scientist
[email protected]