Mottelson, Ben Roy (1926-2022), an American-born Danish physicist, studied the structure of the atomic nucleus and showed that nuclei are not perfectly spherical, as had been previously believed. He was awarded the 1975 Nobel Prize for physics, sharing it with Aage N. Bohr of Denmark and L. James Rainwater of the United States. 
Mottelson was born in Chicago on July 9, 1926. He graduated from high school during World War II (1939-1945) and was sent by the U.S. Navy to Purdue University in Indiana for officer training. He remained there after the war to complete his bachelor’s degree. In 1947, he went to Harvard University in Cambridge, Massachusetts, to study nuclear physics for a Ph.D. degree. Mottelson completed his Ph.D. in 1950.
Mottelson gained a fellowship from the U.S. Atomic Energy Commission, which allowed him to carry on research with CERN (the European Organization for Nuclear Research) in Geneva, Switzerland, from 1953 to 1957. In 1957, Mottelson became a professor at the Nordic Institute for Theoretical Atomic Physics in Copenhagen, Denmark.
Mottelson became a Danish citizen in 1971. He died on May 13, 2022.
See also Atom (The parts of an atom); Nuclear physics.
