The newly discovered satellite has an estimated diameter of 38 km (23.6 miles) and a magnitude of V 28, likely making it the faintest satellite ever discovered around a trans-Neptunian object.
This image of Quaoar and its moon Vevot was taken by the NASA/ESA Hubble Space Telescope on February 14, 2006. Image credit: NASA/ESA/Hubble/Michael E. Brown.
Discovered June 4, 2002 Quaoar is a trans-Neptunian object with a diameter of about 1,100 km (690 mi).
Like the dwarf planet Pluto, this object lives in the Kuiper belt, an icy field of debris from comet-like bodies.
Also known as 2002 LM60, it orbits 45.1–45.6 astronomical units (AU) from the Sun and has an orbital period of 284.5 years.
In 2006, astronomers discovered Quaoar's moon, Veywot, 80 km (50 mi) in diameter and orbiting at 24 Quaoar radii.
More recently, they discovered two rings around Quaoar, called Q1R And Q2R.
“Over the past decade, stellar eclipses have revealed the presence of rings around small bodies,” said Florida Space Institute astronomer Benjamin Proudfoot and his colleagues.
“Among these small body ring systems, the rings around Quaoar are perhaps the most mysterious.”
“The two rings discovered so far are well beyond the Roche limit and are heterogeneous.”
“Quaoar's outer ring, dubbed Q1R, is at least partially constrained by mean motion resonances with Quaoar's moon Vevot, as well as spin-orbit resonances with Quaoar's triaxial form.”
“The inner ring—Q2R—appears to be less dense and its confinement more uncertain.”
“Recently, during a stellar eclipse, the simultaneous shutdowns of two telescopes revealed the presence of a previously undiscovered satellite or dense ring around Quaoar.”
“The duration of the fall implied a minimum diameter/width of 30 km.”
An artist's impression of a Quaoar and his two rings. Quaoar's moon Vevot is shown on the left. Image credit: ESA/Sci.News.
In their new study, astronomers sought to characterize the orbit of this new satellite candidate.
They found that the object is likely in a 3.6-day orbit, corresponding to an average 5:3 motion resonance with Quaoar's outermost known ring.
They also considered the possibility of observing the satellite during further stellar eclipses.
“Quaoar will remain in the Scutum star cloud for another 10 years, providing the best opportunity for eclipses during its 286-year orbit,” they said.
“Modern ground-based and space-based telescopes will have difficulty detecting the newly discovered satellite due to its weakness (9-10 magnetic magnitudes weaker than Quaoar) and its small angular distance from Quaoar.”
“Our examination of Webb/NIRCam images of the Quaoar system did not reveal a conclusive detection of the satellite,” they noted.
“Direct imaging with existing tools would require a significant investment of telescope time to blindly reconstruct the satellite's phase, if it could actually be detected.”
“However, future generation telescopes will probably be able to observe it easily.”
According to the team, the discovery of the new moon proves that the rings around Quaoar may have been part of an originally wide impact disk that has changed significantly since its formation.
“Studying the formation and history of the lunar disk system will provide detailed insight into the formation of trans-Neptunian objects,” the researchers said.
“We encourage complex tidal, hydrodynamic and collisional modeling of the Quaoar system.”
teams paper was submitted for publication in Letters in an astrophysical journal.
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Benjamin Proudfoot etc.. 2025. Orbital signature of a newly discovered small moon around Quaoar. ApJLin print; arXiv: 2511.07370
