11/mar/22 – Formation of moonlets confining the arcs of Neptune (MSc Gustavo Madeira, GDOP/UNESP)

The arcs of Neptune – Fraternité, Egalité, Liberté, and Courage – are four incomplete rings immersed in the Adams ring. A recent confinement model for the arcs proposes that the structures are azimuthally confined by four co-orbital moonlets. In this work, we intend to approach some points related to the dynamics of co-orbital moonlets and suggest a model for their formation. We study the equilibrium configurations for 1+N co-orbital satellites under the 42:43 Lindblad resonance with Galatea. We obtained three distinct configurations with 1+3 and 1+4 moonlets able to confine and reproduce the location of the arcs. The moonlets’ formation is analysed by the disruption of an ancient body at a Lagrangian point of a moon. The disruption fragments spread out in horseshoe orbits and collide to form moonlets, which reach an equilibrium configuration due to a non-conservative effect. A family of co-orbital satellites azimuthally confining the arcs is an interesting model, since different sets of moonlets, in number, mass, and location can roughly reproduce the width of Neptune arcs. If these satellites exist, the disruption of an ancient body at a Lagrangian point of the moon is a possible model for their formation. The arcs likely formed through a mixture of different processes, with impacts between disruption outcomes and meteoroid impacts with the moonlets being possibilities. The arcs would have larger particles in the past, being the arcs composed only of dust particles, the final stage in an arc lifetime.