Coyne's research interests were in polarimetric studies of the interstellar medium, stars with extended atmospheres, and Seyfert galaxies, which are a class of spiral galaxies with very small and unusually bright star-like centers. Polarimetry studies can reveal the properties of cosmic dust and synchrotron radiation regions in galaxies and other astronomical objects. In later years he studied the polarization produced in cataclysmic variable stars, or interacting binary star systems that give off sudden bursts of intense energy, and dust about young stars. The asteroid 14429 Coyne is named for him.