Testing Strong Gravity with Radio Pulsars

Neutron stars have gravitational binding energy that is roughly 20% of their mass, making these compact objects suitable for tests of gravity inaccessible in the Solar System.  These tests can be carried out using radio-emitting neutron stars, known as pulsars, in binary systems.  Examples of these tests include limits on violation of general-relativistic equivalence principles, on the existence of dipolar gravitational radiation and on variation of Newton's constant.  A few prized pulsars are found in close orbits around other neutron stars, and these highly relativistic systems allow multiple self-consistency tests of gravitational theories, with general relativity still spectacularly compatible with even the tightest constraints.