## Alexandre Correia

## Chaotic rotation for the small moons of the Pluto-Charon system

Circumbinary bodies are objects that orbit around a more massive binary system. Contrarily to the classical two-body problem, circumbinary bodies in planar quasi-circular orbits can present stable non-synchronous resonant rotation. In addition, when the natural rotational libration frequency has the same magnitude as the orbital forcing, the individual resonances overlap and the rotation becomes chaotic. We apply these results to the small moons in the Pluto-Charon system.

Joint work with A. Leleu (Obs. Paris / CIDMA) and P. Robutel (Obs. Paris).

Joint work with A. Leleu (Obs. Paris / CIDMA) and P. Robutel (Obs. Paris).

Carlos Herdeiro

## Black hole shadows

The shadow of a black hole is its silhouette when the black hole is placed in front of a bright background. Its shape depends on the gravitational lensing of light in the vicinity of the black hole, and hence on the spacetime geometry. Thus ongoing and future observations of these shadows will yield information about the true nature of astrophysical black hole candidates. I will review the concept of black hole shadows and lensing of light by black holes using backwards ray tracing techniques and present results for a new type of black holes ("hairy" black holes) which are compared to the paradigmatic black holes in GR.

Joint work with P. V. Cunha, E. Radu and H. Rúnarsson

Joint work with P. V. Cunha, E. Radu and H. Rúnarsson