Neutron Stars as a Laboratory for Dense Matter

Neutron stars provide an exciting laboratory for the physics of matter at extreme conditions. In the first part of this talk, I show how neutron star mass and radius measurements provide a constraint on the equation of state of matter, moving us closer to the elusive answer to the question, "What are neutron stars made of?" The first quantitative statistical analysis the equation of state constraints will be presented, and I will show that several oft-used theoretical models are ruled out by the data. The connection to current terrestial experiments will also be highlighted. In the second part, I describe how obseevations of the cooling of isolated neutron stars are providing new constraints on the nature of pairing among neutrons at high desnities.