On this day, 38 years ago, on February 12, 1987 (January 15, 1987 in the lunar calendar), Soviet astrophysicist Jakov Zeldovich passed away. Zeldovic was born in 1914 in Minsk (present-day capital of Belarus). He studied at Leningrad University and went to work at the Institute of Chemical Physics of the Soviet Academy of Sciences in Moscow after graduating in 1931. Zeldovich engaged in nuclear physics research in his early years and participated in the Soviet Union's hydrogen bomb development program. In the 1950s, Zeldovich's research fields turned to cosmology and particle physics, and in 1958 he became a member of the Soviet Academy of Sciences. He was one of the first to propose that the energy in active galactic nuclei comes from supermassive black holes. In 1964, Zeldovich proposed that the Milky Way X-ray source was produced by the accretion process of a neutron star or black hole in a binary star system. In the same year, he also proposed the existence of cosmic microwave background radiation. In 1972, he and Rashid Sunyayev predicted the influence of galaxy clusters on background radiation. This phenomenon was named the Sunyaev-Zeldovich effect, which can be used to measure the distribution of matter in galaxy clusters, the value of Hubble's constant, etc. He passed away on February 12, 1987.