Freeman is distinguished for his theoretical and observational studies of star clusters and of galaxies. His construction of the first self-consistent model of rotating barred galaxies was a notable achievement in stellar dynamics, while his discovery of a general property of spiral galaxies, that their surface brightness falls off exponentially with radius, is the most important in its field for many years and has become a major cosmoganic problem. He devised the first accurate method for measuring the masses of globular clusters, and his recent discovery that at least some globular clusters are not chemically homogenous
has major implications.
Freeman is a true leader in that his main papers are already classical and have opened up lines of work which are being followed by many investigators in many observatories.