The hypnotic dance of Patroclus and Menoetius: Ground-based observations of their 2017-2018 mutual event season.

Pinilla-Alonso, Noemí; Popescu, Marcel; Fernández-Valenzuela, Estela; Licandro, Javier; Duffard, René; Castro, Joel; Murillo, Raúl M.; Grundy, William; Reyes-Ruiz, Mauricio; Silva, José
Referencia bibliográfica

American Astronomical Society, DPS meeting #50, id.200.02

Fecha de publicación:
10
2018
Número de autores
10
Número de autores del IAC
2
Número de citas
0
Número de citas referidas
0
Descripción
Trojans are a significant portion of the small bodies population located within two clouds in the L4 and L5 Lagrangian points of Jupiter's orbit. The study of primitive small bodies is relevant to the origin and nature of volatile and organic material in the early Solar System. Dedicated studies of the nature of these bodies can significantly improve our understanding of their nature, origin and evolutionary mechanisms. Lucy, a mission of the NASA's Discovery Program, is planned to launch in October 2021 for a 12-year journey. Lucy will explore seven different primitive small bodies, six of which will be Trojans. The mission will use a suite of remote sensing instruments to map the geology, surface color, composition, thermal and other physical properties of the targets at close range. Our international team performed observations during 2017 and 2018 to record the light-curve of the mutual events of the binary system formed by Patroclus and Menoetius, providing a unique opportunity to refine their orbit characteristics as well as other properties of the system (sizes, shape, and mass of both objects). Patroclus is the first binary trojan to be discovered. Previous studies by Marchis, et al. (2016, Nature, 439) determined the mutual orbit of the system to have a period of 4.283 ± 0.004 days and a semimajor axis of 680 ± 20 km, leading to a system mass of (1.36 ± 0.11) x 1018kg and an average bulk density of 0.8 ± 0.2 g cm-3. When the plane of their mutual orbit is aligned with the direction to the Sun or to an observer, Patroclus and Menoetius take turns eclipsing or occulting one another. Such an alignment occurs during mutual event seasons, twice during the ˜12 year orbit around the Sun. We show, for the first time, a collection of light-curves that are the result of about 20 detections. Our analysis puts a special focus on the differences between the observations and the models of the orbit (Grundy et al. 2018, Icarus 305) providing unique and crucial information that includes the possible topographic variation on Menoetius' south pole, a refinement to the orbit model, and improved predictions for shadowing and occultation events.