Neutron stars are compact objects with masses comparable to the Sun’s, but radii of roughly 10 kilometers. Their internal densities exceed that of nuclear matter. Their gravitational fields are the strongest in the Universe, except for those of black holes. Their magnetic fields are extreme, maybe reaching 10^{16} Gauss in magnetars. With spin periods anywhere from milliseconds to seconds, these neutron stars emit radiation in the radio band that reach Earth every time the radiation beams across Earth’s line of sight. These pulses of radiation have led to precise timing of the spin period of pulsars, their motion if in binary systems, and tests of General Relativity.

At the XGI, we study neutron stars, their internal composition, their magnetic fields and their potential use as probes of extreme gravity. For example, through binary pulsar timing, these objects can be used to tests General Relativity to some of the most stringent levels, orders of magnitude more strongly than in the Solar System.