Soviet-Armenian astronomer who in 1955 proposed the manner in which enormous catastrophes might take place within stars and galaxies during their evolution. Ambartsumian was born in Tiflis (now Tbilisi), Georgia, and studied at the University of Leningrad, where he later taught.
In 1944 he was appointed head of the Byurakan Observatory in Yerevan, Armenia. The radio source in Cygnus had been associated with what appeared to be a closely connected pair of galaxies, and it was generally supposed that a galactic collision was taking place. If this were the case, such phenomena might account for many extragalactic radio sources. However, Ambatzumian presented convincing evidence in 1955 of the errors of this theory.
He suggested instead that vast explosions occur within the cores of galaxies, analogous to supernovae, but on a galactic scale.
His book Theoretical Astrophysics 1939 was influential.