Ambartsumian's life spanned the whole period of existence of the USSR and illustrates both the difficulties of working under that system and the remarkable talents necessary to surmount them. He founded a flourishing school of astronomy in Armenia and the Byurakan Observatory. Within the Soviet Union his political skills made him a member of the Supreme Soviet and one of the most powerful scientists of his time. In astronomy, he discovered basic results in the theory of the transfer of radiation through matter. He discovered stellar associations and showed that most stars were born in such unbound expanding associations rather than in bound clusters. He came to believe, therefore, that stars were born explosively. Extending this to galaxies, he was the first to emphasize the importance of activity and explosions in the nuclei of galaxies long before quasars and black holes were discovered there. He was a pioneer of astronomical research from Soviet spacecraft.