1905 Ambartsumian, provisional designation 1972 JZ, is an asteroid from the inner regions of the asteroid belt, approximately 8 kilometers in diameter. It was discovered on 14 May 1972, by Russian astronomer Tamara Smirnova at the Crimean Astrophysical Observatory, Nauchnyj, on the Crimean peninsula.
The asteroid orbits the Sun at a distance of 1.9–2.6 AU once every 3 years and 4 months (1,211 days). Its orbit has an eccentricity of 0.16 and an inclination of 3° with respect to the ecliptic. It was first identified as 1932 FC at Simeiz Observatory in 1932, extending the body's observation arc by 40 years prior to its official discovery observation.
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Ambartsumian measures 8.0 kilometers in diameter and its surface has an albedo of 0.23. When using a generic diameter-to-magnitude conversion, it has a diameter of 7–17 kilometers, based on an absolute magnitude of 12.8 and an albedo in the range of 0.05–0.25, which accounts for both the brighter stony as well as for the darker carbonaceous spectral types. As of 2016, Ambartsumian's composition, rotation period and shape remain unknown.
The asteroid was named after Soviet–Armenian scientist Victor Ambartsumian (1908–1996), founder of the Soviet School for Astrophysics, president of the Academy of Sciences of the Armenian SSR, director of the Byurakan Observatory, and president of the IAU (1961–1964). Naming citation was published before November 1977 (M.P.C. 3937).