Today Michele Bannister (Belfast) gave a great talk about the outer Solar System. She was very clear that her observations do not rule out in any way the existence of Planet 9. But they do discredit every single shred of evidence in its favor! And she gave many other mechanisms that could explain the same data. That is, there really doesn't seem to be any reason to believe that there is an unknown planet hanging out in the outer Solar System. Lots of what she said relies on the following theoretical observation: When a planetesimal is perturbed by a massive body on an orbit interior to its perihelion, it tends to preserve its perihelion but change its semi-major axis. And the same but opposite when the massive body is outside it's aphelion. All planetesimal migration scenarios must respect these constraints.
Before that, Kate Storey-Fisher (NYU) and I had a long conversation in which we re-discovered our confusions about the differences between the continuous Fourier transform (which never exists in any real-data context) and the discrete Fourier transform (which is what's appropriate when the data are treated as a patch of a periodic function. We got confused and then un-confused, but I am still somewhat confused!
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