The rich harvest of stellar occultations: rings, atmospheres and other treats

23/06/2021 - 14:00 - 15:00
Remoto, com transmissão pela internet



The rich harvest of stellar occultations: rings, atmospheres and other treats

Bruno Sicardy

Université Pierre et Marie Curie/Observatoire de Paris

My ERC Advanced Grant project 'Lucky Star' (2015-2021) aims at exploring our solar system using stellar occultations. It involves both professional and amateur scientists from Brazil, Spain and France. The project was started before the ESA/Gaia spacecraft released its astrometric catalogs and before the NASA/New Horizons flew by Pluto and the remote Arrokoth. The release of the Gaia DR1 (2016) and DR2 (2018) catalogs boosted the prediction accuracies, down a few milli-arcsec (mas) accuracy for many objects. This completely changed our approach paradigm, as we can now focus on the science, rather than picking up any possible (and not necessarily important) events. The New Horizons Pluto flyby, on the other hand, provided a remarkable illustration of how tightly complementary are Earth and space observations. The Lucky Star harvest is rich, with the discovery of a ring around the dwarf planet Haumea, unprecedented detailed observations of Chariklo's rings, the monitoring of Pluto's climate, the spectacular central flashes observed during a Triton occultation in 2017, and the sizes and shapes of various objects (Haumea, Huya, Quaoar, Varda, Bienor, among others). The Lucky Star project also triggered theoretical studies in various areas, e.g. in ring dynamics, climatic cycle on Triton and Pluto, modeling of dwarf planet interiors such as Haumea's, etc... that I will briefly review.


Bruno Sicardy is the co-discoverer of the incomplete Neptune's ring arcs (1984), as well of the rings around the small Centaur objects Chariklo (2013) and the dwarf planet Haumea (2017). He also unveiled the spectacular increase (by a factor of three) of Pluto's atmospheric pressure between 1988 and present time. Prof. Sicardy measured the size of the most remote body presently observable in the solar system, the dwarf planet Eris (2010), at km-accuracy, and Saturn's ring thickness (1980). Besides observational results, he works on theoretical problems involving dynamics of disks, in particular the effects of resonances between collisional rings and perturbing satellites.


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