Weywot, an Unusually Low-albedo Satellite in the Trans-Neptunian Region

Abstract Weywot is the largest satellite of the candidate dwarf planet Quaoar, which also hosts a remarkable ring system located beyond its Roche limit—a configuration that challenges conventional understanding of ring dynamics. In this work, we predicted three stellar occultations by Weywot occurring in 2023 May and June, of which one was successfully observed on 2023 June 22. This multichord event took place over North America, where observers were deployed across the shadow path from Maryland to California. Five positive detections and two near misses allowed us to accurately constrain Weywot’s projected size and shape at the time of the occultation. We constrained the equivalent diameter to be between 116 and 172 km (with 95% confidence) and estimate a geometric albedo between 0.024 and 0.078—substantially lower than that of Quaoar. These results offer new insights into the physical properties of Quaoar’s system and provide valuable constraints for models of its formation and evolution.