Career
His last name is also alternatively spelled Beljavskij (name under which the Minor Planet Center credits him) or Beljawskij. His first name is occasionally given as "Sergius". His field of work included astrophotometry, astrometry, and the study of variable stars.
He died in Leningrad.
He discovered the bright naked-eye comet C/1911 S3 (Beljawsky), also known according to the nomenclature of the time as "Comet 1911 IV" or "Comet 1911g". Belyavsky observed at Simeiz Observatory (Симеиз) in Crimea.
Between 1937 and 1944, Belyavsky was the seventh director of the Pulkovo Observatory, where he succeeded Boris Petrovich Gerasimovich.