Key scientific investigations selected for the proposed Advanced X Ray Astrophysics Observatory (AXAF), which will make detailed observations of X ray emissions from such sources as stars and quasars, were announced recently by the National Aeronautics and Space Administration (NASA).Investigations selected include charged coupled device imaging spectroscopy, high throughput transmission grating for cosmic X ray spectroscopy, the coronal structures of selected cool stars and close binary systems, studies of radio jets and the narrow line regions of active galaxies with AXAF, and cooling flows in clusters and galaxies.