#Eclipse2017

I just returned from an off-grid eclipse trip; hence no posting. Also, it was vacation! The total eclipse (which I saw in central Oregon) was extremely dramatic: The air got cold, the sky got so dark we could see the stars, and there was a quasi-sunset around all the horizon. The corona of the Sun could be seen, during totality, out to more than a Solar Diameter off the limb of the Sun. During late stages of partiality, the shadows created an amazing demonstration of the sense in which a shadow is a convolution of a mask with the illumination, and how that convolution depends on distance (between the object and its shadow). I have much more to say about all this (and photographs), but I will save it for one of my other blogs!

The only research I did during the week was discussion of near-term projects with Bernhard Schölkopf (MPI-IS) and Hans-Walter Rix (MPIA), which will involve building latent-variable models (and related things) on stellar spectra. In some down time, Schölkopf also helped me with some non-trivial linear algebra!

the best temperature-gravity relationship ever

We have realized that Anna Ho has the most detailed, feature-rich diagram of the temperature–gravity relationship for red giant stars ever created. She has 450,000 red giants from LAMOST labeled with APOGEE and The Cannon. None of these giants is supremely precisely labeled with either temperature or gravity, however, the sheer numbers make for visibility of very subtle features in the diagram that have (perhaps) never been seen before. Anna made visualizations and a gif of the data, and we debated what to do about it all, in the next paper. We are trying to get papers one and two done first.

I performed a code review with Melissa Ness, and we were able to speed up her code by a significant factor. We did it by reducing functionality, of course! But now she can run experiments fast, which is critical in the investigation phase. We made predictions for the figures she should make and what they would look like. She is working on putting far more informative prior beliefs into The Cannon.

Late in the day came the Physics Research Conference (Colloquium). It was by Maria Zuber (MIT), talking about the GRAIL mission to map the geoid of the Moon. The mission was amazingly simple: Two satellites in low orbit around the Moon, sending time-codes to each other and back to Earth. Do the math and figure out the gravitational shape of the Moon. She had many geological (or selenological?) results to discuss. In particular, she has an explanation for the strong morphological differences between the front side and the back side of the Moon. I was impressed that the data analysis was not in the slightest probabilistic: They just did the GPS-like thing (GRAIL is very like a miniature GPS) of finding the best solution to explain the data. It made it clear that a better analysis is possible. Not that I'm volunteering!