Stability of prograde and retrograde planets in binary systems

M. H. M. MORAIS , C. A. GIUPPONE

Serra Negra, Sao Paulo

Congreso; XVI Colóquio Brasileiro de Dinâmica Orbital; 2012

Universidade Federal do ABC

We will present results of a recently published article [1] where we investigate stability of coplanar prograde and retrograde planet orbits within binary systems. There were previous numerical stability studies regarding prograde planets but retrograde planets were never investigated before. However, retrograde planets within binary systems could form via Kozai interaction with the companion star or via capture from a passing star. Contrary to previous works, we will not only perform simulations but we will also provide theoretical explanations for the onset of instability. We will show that retrograde planets are stable up to distances much closer to the companion star than prograde planets. We will prove that instability is due to mean motion resonances (MMRs), either eccentricity forcing at individual MMRs or caused by overlap of nearby MMRs. We will conclude that the observed enhanced stability of retrograde planets with respect to prograde planets is due to essential differences between the phase-space topology of retrograde versus prograde resonances (p/q prograde MMR is of order p-q while p/q retrograde MMR is of order p+q).