Evidence for a rapid decrease in Pluto's atmospheric pressure revealed by a stellar occultation in 2019

Abstract

We report observations of a stellar occultation by Pluto on 2019 July 17. A single-chord high-speed (time resolution $=2$s) photometry dataset was obtained with a CMOS camera mounted on the Tohoku University 60 cm telescope (Haleakala, Hawaii). The occultation light curve is satisfactorily fitted to an existing Pluto's atmospheric model. We find the lowest pressure value at a reference radius of $r=1215\mathrm{km}$ among those reported after 2012, indicating a possible rapid (approximately $21_{-5}^{+4}\%$ of the previous value) pressure drop between 2016 (the latest reported estimate) and 2019. However, this drop is detected at a $2.4\sigma$ level only and still requires confirmation from future observations. If real, this trend is opposite to the monotonic increase of Pluto's atmospheric pressure reported by previous studies. The observed decrease trend is possibly caused by ongoing ${\mathrm{N}}_2$ condensation processes in the Sputnik Planitia glacier associated with an orbitally driven decline of solar insolation, as predicted by previous theoretical models. However, the observed amplitude of the pressure decrease is larger than the model predictions.

7 pages, 3 figures, accepted for publication in Astronomy and Astrophysics

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• Reconciling results of 2019 and 2020 stellar occultations on Pluto's atmosphere. New constraints from both the 5 September 2019 event and consistency analysis
• Study of Pluto's Atmosphere Based on 2020 Stellar Occultation Light Curve Results
• Reaching sub-millisecond accuracy in stellar occultations and artificial satellites tracking
• Changes in Pluto's Atmosphere Based on Stellar Occultation Data from 2017 to 2023
• Pluto's atmosphere observations with ALMA: spatially-resolved maps of CO and HCN emission and first detection of HNC