Study of Pluto’s atmosphere based on 2020 stellar occultation light curve results

Abstract

On 6 June 2020, Pluto's stellar occultation was successfully observed at a ground-based observatory in Iran, and Pluto's atmospheric parameters were investigated. We used an atmospheric model of Pluto, assuming a spherical and transparent pure N 2 atmosphere. Using ray-tracing code, the stellar occultation light curve was satisfactorily fit to this model. We found that Pluto's atmospheric pressure at the reference radius of 1215 km was 6.72 ± 0.48 µbar in June 2020. Our estimated pressure shows a continuation of the pressure increase trend observed since 1988 and does not confirm the rapid pressure decrease tentatively reported in 2019. The pressure evolution is consistent with a seasonal transport model. We conclude that the N 2 sublimation process from Sputnik Planitia is continuing. This study's result is shown on the diagram of the annual evolution of atmospheric pressure.

Pluto's atmosphere in plateau phase since 2015 from a stellar occultation at Devasthal

“…Besides the observations presented here, the 6 June 2020 event was observed by an independent team, see Poro et al (2021). The event was observed at low elevation (6 degrees) near the city of Karaj in Iran with a 60-cm telescope.…”

“…2) onto the results of Poro et al (2021) (black curve), we see a clear discrepancy between our models in the deepest part of the occultation. This shows that the ray tracing code of Poro et al (2021) is inconsistent with ours. Consequently, the results of Poro et al (2021) are impossible to obtain considering their published light curve, and probably stems from improper use of their ray-tracing code.…”

“…By shrinking the time scale in an attempt to superimpose our model (green curve in Fig. 2) onto the results of Poro et al (2021) (black curve), we see a clear discrepancy between our models in the deepest part of the occultation. This shows that the ray tracing code of Poro et al (2021) is inconsistent with ours.…”

“…However, their derived value p surf = 12.36±0.38 µbar, is questionable. First, the time axis for the Karaj light curve in Poro et al (2021) is wrong by a large factor of about two, see Fig. 2.…”

“…This makes impossible to obtain any realistic value of p 1215 from this light curve. Secondly, assuming that the Karaj time axis has some (undocumented) problems, considering the occultation geometry at that station and adopting the p 1215 = 6.72 µbar value of Poro et al (2021), we generated a synthetic model using our own ray-tracing code. By shrinking the time scale in an attempt to superimpose our model (green curve in Fig.…”