OBITUARY : Victor Ambartsumian

Within the Soviet Union Victor Ambartsumian pursued twin careers as both a leading astronomer and a powerful politician who rose to represent his native Armenia as a deputy in the Supreme Soviet of the USSR.

Born in Tblisi, Georgia in 1908 and educated in Leningrad, his work first came to prominence in physics when in 1929 with Dmitry Ivanenko he published a paper demonstrating that atomic nuclei could not be made from protons and electrons. Three years later this was confirmed when Sir James Chadwick discovered neutrons, which with protons make up atomic nuclei.

Ambartsumian worked for some years at the Pulkovo Observatory, near Leningrad, where he turned his attention to the transfer of radiation through stellar atmospheres in the approximation where the curvature of the stratification is neglected. There he discovered an important new invariance principle later taken up by Subrahmanyan Chandrasekhar, and demonstrated his formidable powers in analytic mathematics.

Thus he was already well known internationally when in 1943 he moved back to his native Armenia to found the world-famous Biurakan Observatory in 1944 (he remained its Director until 1988) on Mount Aragats, north of Yerevan, the Armenian capital, and to become Professor of Astrophysics at Erevan University in 1947.

Here he developed the idea that explosions from a very dense state are associated with the formation of stars, star clusters, galaxies and even the universe itself. He showed that most young stars are not gravitationally bound in clusters but are members of expanding associations, and this was soon widely accepted. He regarded this expansion as a relic of the creation process and looked for explosions as a sign of creation in all astronomical objects from flare stars to galaxies and the universe.

Explosions in galactic nuclei and quasars are now widely accepted phenomena and while these were certainly predicted by Ambartsumian's ideas, those ideas themselves are not widely held. Nevertheless it was his relentless quest to get evidence to further these ideas concerning astronomical explosions that led him to push for better equipment for the observatory.

He directed campaigns of discovery and observation of many of the most interesting objects in the sky including flare stars in clusters and associations, active galaxies and quasars. Without the equipment he fought for, such well-known astronomical catalogues of active galaxies as those of Markarian and Arakelian would never have been produced and Gurzadian's studies of flare stars could not have been made.

Ambartsumian put Armenia on the astronomical map. He could never have achieved all this without his skills as a politician. From 1940 he was a member of the Communist Party of the Soviet Union, became president of the Armenian Academy of Sciences 1946-93, served as a Deputy to the Supreme Soviet of the USSR from 1950 and was a member of the foreign affairs committee of the Soviet Union as well as holding similar posts in the Armenian Communist Party. In 1989, when aged 80, he went on a three- week hunger strike to attract the Soviet government's attention to the Nagorny Karabakh enclave's drive to secede from Azerbaijan and join Armenia.

He was twice a Hero of Soviet Labour and held the Hammer and Sickle Gold Medal and five Orders of Lenin among other Communist awards. He was president of the International Astronomical Union 1961-64 and of the International Council of Scientific Unions 1968- 72.

His many academic honours include membership of the USSR Academy of Sciences, and foreign membership of the Royal Society, the US National Academy and the Indian Academy of Sciences. After the collapse of the Soviet Union he was awarded the medal of a National Hero of Armenia.

Victor Ambartsumian was a broad-shouldered thickset man of medium height, quick intellect and strong character. It was best to have him on your side in any argument. His love of poetry and music was shared with his wife Vera.

Victor Amazaspovich Ambartsumian, astrophysicist and politician: born Tblisi, Georgia 18 September 1908; lecturer and research worker, Leningrad University 1931-43; corresponding member, USSR Academy of Sciences 1939- 53, member 1953-96; member, Communist Party of the Soviet Union 1940-96; member, Armenian Academy of Sciences 1943-96, President 1947-93, Honorary President 1993-96; Founder and Director, Biurakan Astrophysics Observatory 1944-88; Professor of Astrophysics, Erevan University 1947-96; Vice-President, International Astronomical Union 1948-55, President 1961-64; Deputy, Supreme Soviet USSR 1950-91; President, International Council of Scientific Unions 1968- 72; married 1931 (two sons and two daughters); died Mount Aragats, Armenia 12 August 1996.