SFoA, day 4

Today was exoplanet day at the SFoA meeting, which meant I learned the most. Among other things, Winn (MIT) told us that he can measure the alignments of planetary orbits with stellar rotation and that planet transits more-or-less directly tell you the surface gravity on the planet. Turner (Princeton) spoke about strong biases in fitting planets to radial velocity curves, which emerge from the nonlinearity of the fitting. Laredo (Cornell) showed a system for optimizing or guiding future radial velocity measurements given measurements in the past, where he is optimizing for information gained about the orbit. As he points out, you can optimize for many things there; it is a multi-armed bandit kind of problem. One thing that surprised me is that he takes the convergence of his MCMC chains very seriously, which is good in general, but does not seem necessary to me in order to perform these experimental design activities. After all, your utility will always be approximate, why spend millions of hours of CPU time to fill out in enormous detail predictions of future trajectories that will only be used to approximately calculate your utility? But he is certainly thinking about the problems the right way.

Several mentioned that although orbit fitting is now being performed in quasi-optimal ways, the original data reduction (going from spectral pixels to radial velocity measurements with errors) is not. Turner opined that if this were done better, more planets would be discovered, because there are many detections close to the current limits. That's a big—but very important—problem.