The Sunyaev–Zeldovich effect is the spectral distortion of the cosmic microwave background (CMB) through inverse Compton scattering by high-energy electrons in galaxy clusters, in which the low-energy CMB photons receive an average energy boost during collision with the high-energy cluster electrons. Observed distortions of the cosmic microwave background spectrum are used to detect the disturbance of density in the universe. Using the Sunyaev–Zeldovich effect, dense clusters of galaxies have been observed.

Rashid Alievich Sunyaev is a German, Soviet, and Russian astrophysicist of Tatar descent. He got his MS degree from the Moscow Institute of Physics and Technology (MIPT) in 1966. He became a professor at MIPT in 1974. Sunyaev was the head of the High Energy Astrophysics Department of the Russian Academy of Sciences, and has been chief scientist of the Academy's Space Research Institute since 1992. He has also been a director of the Max Planck Institute for Astrophysics in Garching, Germany since 1996, and Maureen and John Hendricks Distinguished Visiting Professor in the School of Natural Sciences at the Institute for Advanced Study in Princeton since 2010.