It was my pleasure to sit on the PhD defense committee of Gregory Green (Harvard) today. I had to do it remotely (for uninteresting reasons). Green has built a three-dimensional map of the dust in the Milky Way, by modeling every single star in the PanSTARRS data. This is an impressive feat computationally, since it is a huge problem, and also probabilistically, since most things you can write down are either intractable or wrong.
Being a good probabilistic reasoner, Green did something both tractable and correct, and got a beautiful map. His tours of the map in his presentation were mesmerizing. He was cagey about spiral structure; his method wouldn't necessarily find it even if it were there.
It was a great PhD defense based on absolutely great work. At the end of his talk he discussed ways he might do things that are even righter in the future, given our prior beliefs about the interstellar medium (and lots of new data). That's super interesting, and we hope to discuss when his dust settles (so to speak). Congratulations Dr Green!