Together with Otto Struve, he studied the rapid rotation of stars of young spectral types and measured the radial velocities of stars.
He discovered new gaseous nebulas and the anomalous abundance of 13C in stellar atmospheres.
He became a member of the Soviet Academy of Sciences in 1939, and was also a member of various foreign societies such as the Royal Astronomical Society.
From 1945 to 1952 he was the director of the Crimean Astrophysical Observatory.
He also discovered a few asteroids.
He also co-discovered the non-periodic comet C/1925 F1 (Shajn-Comas Solá), also known as Comet 1925 VI or Comet 1925a.
However, the periodic comet 61P/Shajn–Schaldach was co-discovered by his wife rather than by him.The crater Shayn on the Moon is named after him.
He and his wife were also honoured by the minor planet 1648 Shajna.