Tateos Artemjevich Agekian was an outstanding Soviet astrophysicist of Armenian descent, one of the pioneers of Russian and world Stellar dynamics. Has found two evolutionary sequences of stellar systems: nearly spherical and strongly flattened. Suggested essentially new method to investigate the structure and kinematics of the Milky Way Galaxy. Found a new estimate for the dissipation rate in stellar clusters. Gave an exhaustive analysis of the photogravitational interaction between stars and gas clouds. A planet was named in honor of Tateos Artemjevich.