Discovery of a New Satellite or Ring Arc around (50000) Quaoar

Abstract On 2025 June 25 UT, a near grazing passage of TNO (50000) Quaoar’s known ring Q1R over a 14.9 mag star was predicted for the Monterey Institute for Research in Astronomy’s Oliver Observing Station (MIRA-OOS) in California. The event was recorded on two MIRA-OOS telescopes by Richard Nolthenius (RN) and Kirk Bender (KB). No opacity due to Q1R was detected, but instead, a complete occultation lasting 1.23 s was recorded 2.4 minutes before the predicted Q1R graze. We argue this was most likely due to a new satellite—inferred magnitude 28—but cannot yet rule out a third ring with opaque arc.