造父变星
During 1999, this galaxy was the subject of an extended study using the Hubble Space Telescope to locate Cepheid variable stars. A total of were found, and the measurement of their periodicity gave a net distance estimate of (). This is consistent with the distance estimate determined through redshift measurements. As of the time of this study, NGC 4603 was the most distant galaxy for which a distance estimate had been made using Cepheid variable.