the Sun is normal; how did Jupiter form?

At group meeting, Wang reviewed Basri, Walkowicz, & Reiners (2013) on the variability of the Sun in terms of Kepler stars. It shows that (despite rumors to the contrary) the Sun is very typically variable for G-type dwarf stars. It is a very nice piece of work; it just shows summary statistics, but they are nicely robust and insensitive to satellite systematics.

Also in group meeting, Vakili showed first results from a dictionary-learning approach to the point-spread function in LSST simulated imaging. He is using stochastic gradient descent, which I learned (in the meeting) is useful for starting off an optimization, even in cases where the full likelihood (or objective) function can be computed just fine.

After lunch, Roman Rafikov (Princeton) gave a nice talk about the formation of giant planets. He argued that distant planets (like in HR 8799) might have a different formation mechanism that close planets (like Jupiter and hot Jupiters). One very interesting thing about planets—unlike stars—is that the structure is not just set by the composition; it is also set by the formation history.