How heavy are heavenly bodies?
Eric Agol

Syzygy alignment with a pair of bodies gives the opportunity to measure their relative size, while in some cases we can also measure mass. I will discuss Kepler measurements of transit timing variations (TTVs) and of a self-lensing binary, and how these phenomena have been used to measure the masses of planets and of a white dwarf. Future TTV measurements with JWST may yield the first density estimates of habitable-zone, potentially rocky exoplanets.