A single-chord stellar occultation by Chariklo's ring system observed from JWST
Session 9.02 Occultations (Targeted)
Thursday 06-27 | 09:30 - 09:50

Perhaps the most surprising discovery in the field of minor body science over the past decade is the identification of rings around the Centaur Chariklo, an object too small to achieve hydrostatic equilibrium. Since that discovery, rings have been identified around another Centaur, Chiron, and the large trans-Neptunian objects Haumea and Quaoar. Minor body ring systems provide important clues to the dynamical and collisional history of the outer solar system, specifically the trans-Neptunian region, as well as the formation mechanism of satellites, a topic opened for debate after the discovery of the ring of Quaoar well outside its Roche limit. Other open questions include the mechanism that confines dense rings and why the three rings discovered so far around small bodies are close to the 1:3 spin-orbit resonance with the primary. In order to further explore minor body ring systems, we predicted and observed a stellar occultation by Chariklo from the James Webb Space Telescope (JWST) on October 18th, 2022 UT. Observations were made as part of Guaranteed Time Observation (GTO) program 1271 using the NIRCam instrument in time series mode. Individual frames were obtained at a cadence of 3.3 Hz simultaneously through the very wide-band F150W2 and F322W2 filters to maximize signal-to-noise. JWST was not in the shadow-path for the solid-body occultation, but drop-outs from the rings on either side of Chariklo were observed. This near-miss placed valuable constraints on the size and shape of Chariklo and the ring occultations revealed weaker ring signatures compared to previous ground-based occultations, which is attributed to the use of longer wavelength filters and grain size effects. This is the first stellar occultation observed from JWST and is a successful proof-of-concept of the feasibility of using JWST to characterize solar system minor bodies and rings using this powerful observational technique.

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