Submitted Abstract
I will investigate the Kepler-56 exoplanetary system and attempt to understand how it formed. The spin-orbit misalignment of the two inner planets with respect to their host star needs an explanation since they can’t have formed this way: it is widely accepted today that planets form in an orbit that lies in the plane of the host star’s spin. In addition, both planets orbit their parent star in the same plane, an observation that disfavors several hypotheses. The potential existence of a third planet acting as a destabilizing factor in the early stages of the planetary system warrants a closer look at the scattering hypothesis. It posits that the outer planet is being scattered into an inclined orbit (by a fourth companion that is ejected? UPDATE: Yes, but need a fifth companion!), and into a substantial eccentricity, which in turn will excite the two inner planets into their observed inclination about 45 degrees off with respect to their star’s equatorial plane. I will test my hypothesis with the help of supercomputers. As an expansion of the project, I generalized the initial configurations and looked at a whole range of closely packed systems over a timescale of several billion years. We now know that many exoplanetary systems exist in such configurations, and a more analytical understanding of whether those systems can remain stable for billions of years is needed. (Kepler-56, for example, is now known to be unstable over those time scales.)In collaboration with Jack Lissauer, I investigate a total of five planets orbiting their host star at (initially) very close orbital periods. We added nonzero initial eccentricities (first paper); we then consider, in addition to nonzero eccentricities, nonzero inclinations (second paper).This will bring us back to the Kepler-56 system and its highly unstable configuration.