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Alexandr Boyarchuk (June 21, 1931 – August 10, 2015) was aRussianphysicist andastronomer.

In 1953, he graduated fromLeningrad University. After graduation, he worked at the Crimean Astrophysical Observatory, which was under direction of the USSR Academy of Sciences at the time. Later, he was elected a corresponding member of the same organization, and worked as an academician there until 1987. From 1987 to 2003, he was the director of theInstitute of Astronomy of the Russian Academy of Sciences. From 1991 to 1993, he was also President of theInternational Astronomical Union.^[1][2]

Boyarchuk specialized in studying the physics of stars. He carried out numerous studies regarding the chemical composition of stars of various classes, in particular, he discovered an excess of helium inBeta Lyrae. Boyarchuk also studied the motion of stellar atmospheres, as well as the rotation of stars. He devoted a number of his works to non-stationary stars. He was the developer of a model of symbiotic stars. Based on this model, he obtained estimates of the mass, size, temperature and other characteristics of these objects. Together with E.R. Mustel, he proposed a model for the envelope of new stars. Under the leadership of Boyarchuk, the ultraviolet telescopeAstron was created.

Boyarchuk died on August 10, 2015, at the age of 84 inMoscow.

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