Today Christina Eilers (MPIA) gave a great colloquium talk at MPIA about the intergalactic medium, and how it can be used to understand the lifetime of quasars: Basically the idea is that quasars ionize bubbles around themselves, and the timescales are such that the size of the bubble tells you the age of the quasar. It's a nice and simple argument. Within this context, she finds some very young quasars; too young to have grown to their immense sizes. What explanation? There are ways to get around the simple argument, but they are all a bit uncomfortable. Of course one idea I love (but it sure is speculative) is the idea that maybe these very young quasars are primordial black holes!
In other research today (actually, I think this is not research according to the Rules), I finished a review of a book (a history of science book, no less) for Princeton University Press. I learned that reviewing a book for a publisher is a big job!