Search for confine material around the TNO (50000) Quaoar

The Trans-Neptunian Object (50000) Quaoar, classified as a cubewano, is a dwarf planet candidate with a diameter of 1110 km, a semi-major axis of 43.7 au, and an orbital eccentricity of 0.04. Its satellite Weywot orbits at 13,300 km from the primary object, and its diameter is about 90 km from its flux, assuming the same albedo as Quaoar. It allows the determination of Quaoar’s mass of 1.20 x 10²¹ kg and bulk density of 2,000 kg.m^-3.

Over the years, several campaigns were conducted within the ERC Lucky Star project to observe stellar occultations by Quaoar and Weywot. Besides measuring Quaoar’s and Weywot’s sizes and shapes, those campaigns aimed at searching for material around this TNO. In this talk, we will present the results of our search for confined material (e.g., rings) around Quaoar based on observations with high photometric accuracy, such as the one observed by the large telescope facility of the Gran Telescopio Canarias (10.4 meters), the CHEOPS space telescope (0.32 meters), and citizen astronomers in Australia and Namibia (between 0.35 and 0.75 meters). The events analysed in this work were observed between 2018 and 2021.

Such rings are already known to exist around other small bodies of our Solar System: the Centaur object Chariklo and the dwarf planet Haumea. In particular, these two ring systems, despite significant differences in sizes and heliocentric distances, both orbit close to the 1/3 Spin-Orbit Resonance (SOR) with the central body, meaning that the latter completes three rotations while a ring particle completes one orbital revolution. That makes the 1/3 SOR location an interesting region for searching for such rings. In particular, considering Quaoar’s rotation period of 17.6788 hours, that will put the 1/3 SOR at about 4,200 km (7.5 Quaoar radii) away from Quaoar’s center, and this would be well outside the Roche limit of the central body of 1.780 km (3.2 Quaoar radii), assuming that the bulk density of particles would be around 400 kg.m^-3 (typical of Saturnian small satellites). This will be discussed in detail during the presentation.

Acknowledgments. The work leading to these results has received funding from the European Research Council under the European Community’s H2020 2014-2021 ERC Grant Agreement no. 669416 “Lucky Star”.