Observatoire de Paris Institut national de recherche scientifique français Univerité Pierre et Marie Curie Université Paris Diderot - Paris 7

Structure and evolution of Triton’s atmosphere using stellar occultations

mardi 16 mars 2021, par Joana Marques Oliveira (LESIA)

Lundi 22 mars 2021 à 16h00 , Lieu : En visioconférence

Triton is the largest of Neptune’s satellites with a radius of 1353 km. It possesses a significant atmosphere, mainly composed of molecular nitrogen N2, that is in vapour pressure equilibrium with the N2 frost at the surface. Between 1990 and 2010, an “extreme solstice” occurred, where latitudes of up to 50º S were directly and constantly illuminated by the Sun. This occurs only every 650 years, due to a combination of Neptune’s heliocentric motion and Triton’s orbital precession. In this talk, we will be discussing the few stellar occultations by Triton that have been observed. We will particularly focus on the event of the 5 October 2017, observed from Europe, north Africa, and USA. This event yielded 90 positive light curves, making it the most observed event of Triton. Our work focused on constraining the evolution of Triton’s atmospheric pressure since the Voyager 2 epoch, as well as deriving the shape of the lower atmosphere from the analysis of the 25 central flashes obtained. We will show the results obtained for the pressure in 2017, and discuss if there has been a surge during the extreme solstice. We also present a new analysis of the original Voyager 2 data, where we were able to extract new information.