Astronomers have discovered a trans-Neptunian object (TNO) named 2020 VN40, which is locked in a unique 10:1 orbital resonance with Neptune, meaning it completes one orbit around the Sun for every ten orbits Neptune makes. This translates to an orbit of about 1,648 Earth years. Unlike other TNOs, 2020 VN40’s highly tilted orbit brings it closest to the Sun when Neptune is nearby, though its steep inclination keeps it far below the solar system’s plane, creating only an apparent proximity when viewed from above. This novel motion, described as “finding a hidden rhythm in a song,” was identified through the Large Inclination Distant Objects (LiDO) survey using the Canada-France-Hawaii Telescope, with support from the Gemini Observatory and Magellan Baade Telescope. The discovery, led by Rosemary Pike from the Center for Astrophysics | Harvard & Smithsonian, suggests Neptune’s gravitational influence extends to highly inclined orbits, offering new insights into the outer solar system’s dynamics and evolution. The Vera C. Rubin Observatory is expected to aid in finding more such objects.
What Makes 2020 VN40 Unique?
While other objects are known to be in orbital resonance with Neptune (like Pluto in a 3:2 resonance), 2020 VN40 stands out due to several factors:
Unusual Resonance Ratio: It's the first object found to have a 10:1 orbital resonance with Neptune. This is a much higher ratio than previously observed for resonant TNOs.
Highly Inclined Orbit: 2020 VN40's orbit is significantly tilted (over 33 degrees) relative to the plane of the Solar System. This high inclination means that even when it makes its closest approach to the Sun (perihelion), it's far "below" or "above" Neptune's orbital plane, preventing any actual close encounters with the ice giant.
Perihelion Alignment: Unlike most other resonant TNOs, which tend to reach perihelion when Neptune is at its furthest point from them, 2020 VN40 reaches perihelion when Neptune is also relatively close to the Sun, though their highly inclined orbits ensure they don't get physically near each other.
Orbital Resonance Explained 💃
Orbital resonance occurs when two orbiting bodies exert regular, periodic gravitational influence on each other, typically because their orbital periods are related by a ratio of small integers. This consistent gravitational tug can lead to stable, synchronized orbital patterns.
A well-known example is the Jupiter Trojans, asteroids that share Jupiter's orbit and are "trapped" in gravitational stability points (Lagrangian points) ahead of and behind the planet. Neptune also has its own Neptune Trojans. However, 2020 VN40's unique 10:1 resonance and its highly inclined orbit set it apart from these previously known co-orbital objects.
Significance of the Discovery 🔭
The discovery of 2020 VN40 is crucial for several reasons:
Understanding Outer Solar System Dynamics: It expands our understanding of how Neptune influences the orbits of distant objects and reveals that even very remote regions can contain objects in complex orbital dances.
Clues to Solar System Evolution: The presence of such an unusual resonant object provides new insights into the processes that shaped the Solar System's early history, including how the giant planets might have migrated and settled into their current orbits.
Novel Orbital Behavior: 2020 VN40 demonstrates a new type of resonant behavior for highly inclined orbits, suggesting that the outer Solar System might harbor many more objects with unexpected movements.
Astronomers are now on the lookout for more bodies like 2020 VN40, with future observatories like the Vera C. Rubin Observatory expected to play a key role in uncovering these hidden rhythms of the Solar System.