AMBARTSUMIAN 14 



and the United States. Ambartsumian has twice received a 

 State Prize, in 1946 and in 1950. He has also received two 

 Orders of Lenin and two Orders of the Red Banner of Labor. 

 In 1961 in Berkeley (USA) V. A. Ambartsumian was elected the 

 President of the International Astronomical Union. 



The early works of Ambartsumian dealt with the study of 

 stellar physics and gaseous nebulae. He has gi'^^en a mathemati- 

 cal interpretation of the complex physical processes involved 

 i-n the luminescence of gaseous nebulae; he has demonstrated 

 the important role of 'L<^' radiation pressure in the nebulae, 

 has developed a solution to the problem of atom accumulation 

 in metastable states, and has elaborated a method for determin- 

 ing the electron temperature of the nebulae. The method he 

 worked out for subdividing the 'Lc' and 'LqI fields of radiation 

 has enabled him to devise a theory of radiation equilibrium of 

 planetary nebulae. This theory has been the foundation for all 

 subsequent studies in this direction, the most valuable of which 

 is the research conducted by his student, V. V. Sobolev. Am- 

 bartsumian has also devised methods of determining the masses 

 of the nebulae and the gaseous envelopes surrounding the stars. 

 These studies have stimulated further research on stellar 

 physics and nebulae both in the Soviet Union and abroad. He 

 was the first in the Soviet Union to have organized a course in 

 Leningrad State University on theoretical astrophysics and is 

 the leader of the Soviet school of theoretical astrophysics. 



More recently Ambartsumian' s interests extended to include 

 stellar astronomy and cosmogony. A large number of his 

 studies deal with the problem of the evolution of stellar sys- 

 tems. The idea underlying these studies is that of the existence 

 of irregular forces in addition to regular forces in stellar 

 systems. In the case of the double stars and star clusters, 

 these irregular forces often play a decisive role in the process 

 of their development. In order to solve this problem, he elabo- 

 rated new methods of statistical mechanics of stellar systems 

 and successfully applied them to dual stars and star clusters. 

 The results of these investigations were incorporated by him 

 into lectures during the 1930' s at Leningrad University. These 

 investigations and other results have affected previously exist- 

 ing theories of the age of the Galaxy and of the evolution of its 

 component systems. Ambartsumian refuted the "Long Time 

 Scale,'' according to which the age of the Galaxy was taken to 

 be roughly lO^^ years, while, according to him, the age of the 

 Galaxy is in the order of 10^0 years. During 1941-43, he 

 personally conducted extensive research on the theory of light 



