Yakov Zeldovich; Boosted Soviet Defense Industry

Yakov Zeldovich, a physicist who played a major role in the Soviet defense industry and helped develop black hole and neutron star theories, has died at the age of 73, Tass said Friday.

Zeldovich died Wednesday, the official Soviet news agency said. It did not disclose the cause of death. The agency said Zeldovich headed the theory department of the Soviet Academy of Sciences Institute of Physical Problems.

Zeldovich made an “immense contribution” in such areas as combustion and detonation theory, the physics of explosions and shock waves, nuclear and elementary-particle physics, gravitation and cosmology, astrophysics and astronomy, Tass said.

“Yakov Zeldovich’s contribution to ensuring the country’s defense capability is inestimable,” it said.

Tass said he had been a member of more than 10 foreign academies and scientific societies.

According to scientific theory, a black hole is a collapsed star that is so condensed that neither light nor matter can escape its gravitational field.