Wunch @ Princeton

Abstract:    Long-term orbital evolution of multi-planet systems under tidal dissipation often converges to a dynamical fixed point. The fixed point is characterized by apsidal alignment among the orbits and lack of variations in the orbital eccentricities. Quantitatively, the nature of the fixed point is dictated by mutual interactions among the planets as well as non-Keplerian effects. The important non-Keplerian effects are general relativity, which dominates for sub-giant planets, and gravitational quadropole fields created by the inner-most planet's tidal and rotational distortions, which dominate for giant planets. If a roughly coplanar, non-transiting system hosts a hot, sub-Saturn mass planet, and is tidally relaxed, separation of planet-planet interactions and non-Keplerian effects in the equations of motion leads to a direct determination of the true masses of the planets. In other words, a "snap-shot" observational determination of the orbital state resolves the sin(I) degeneracy, and opens up a direct avenue towards identification of the true lowest-mass exo-planets detected by radial velocity. On the other hand, in systems where the interior planet is a transiting gas-giant, its fixed-point orbital eccentricity is a strong function of the planet's interior structure and its precise determination can provide an unprecedented probe into the interior structure of an extrasolar planet. Such calculations provide the constraints, needed to understand the degree of interior heating required to explain inflated hot Jupiter radii. I will conclude by discussing Ohmic dissipation as a viable mechanism for inflation of extrasolar gas giants.