Pulsar in binary system may test fundamental theories

A pulsar in orbit about a second compact star would form a very convenient arrangement for studying gravitational interactions and learning the elusive details of the physics of neutron stars. So the announcement by Joseph Taylor and Russell Hulse of the University of Massachusetts, Amherst, that they have observed such a system has been greeted joyfully by general relativists and by astrophysicists who have been longing for a chance to test their models. Studying changes in the pulsar period as the rotating neutron star travels about its companion in a close, highly elliptical orbit should provide checks of time dilatation, precession and perihelion advance effects free of the complications that occur in the weaker gravitational fields of the solar system, perhaps settling the question of which theory of gravitation is the correct one. The changes in period may also yield more details of the structure of pulsars and perhaps even of the nature of the pulsed radiation.