20th-century American astronomers

Eugene Merle Shoemaker (April 28, 1928 – July 18, 1997) was an American geologist. He co-discovered Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy. This comet hit Jupiter in July 1994: the impact was televised around the world. Shoemaker also studied terrestrial craters, such as Barringer Meteor Crater in Arizona, and along with Edward Chao provided the first conclusive evidence of its origin as an impact crater. He was also the first director of the United States Geological Survey's Astrogeology Research Program.
He was killed in a car accident while visiting an impact crater site in Australia. After his death, some of his ashes were carried to the Moon with the Lunar Prospector mission.

Owen Jay Gingerich (; March 24, 1930 – May 28, 2023) was an American astronomer who had been professor emeritus of astronomy and of the history of science at Harvard University and a senior astronomer emeritus at the Smithsonian Astrophysical Observatory. In addition to his research and teaching, he had written many books on the history of astronomy.
Gingerich was also a member of the American Academy of Arts and Sciences, the American Philosophical Society, and the International Academy of the History of Science. A committed Christian, he had been active in the American Scientific Affiliation, a society of evangelical scientists. He served on the board of trustees of the Templeton Foundation.

Albert George Wilson (July 28, 1918 – August 27, 2012) was an American astronomer and a discoverer of minor planets.He was born in Houston, Texas. He received his Ph.D. in mathematics from Caltech in 1947; his thesis title was Axially Symmetric Thermal Stresses in a Semi-Infinite Solid advised by Harry Bateman.
In 1949 he accepted a job at Palomar Observatory, and led the Palomar Sky Survey. In 1953 he became assistant director of Lowell Observatory, and served as director from 1954 to 1957. He later worked at Rand Corporation and other private sector positions. In 1962 he became founding editor of the astronomical magazine Icarus. In 1966, he accepted the position of associate director of McDonnell-Douglas Corporation Advanced Research Laboratories (DARL), which he held from 1966 until 1972. Wilson then became an adjunct professor at USC, teaching courses in philosophy and science until his retirement. After retiring Wilson was associated with the Institute on Man and Science and the Institute of the Future, lecturing and consulting for both groups.He discovered a number of asteroids, and also co-discovered the periodic comet 107P/Wilson–Harrington with Robert George Harrington. The object is also known as the minor planet 4015 Wilson–Harrington.

Trịnh Xuân Thuận (born August 20, 1948) is a Vietnamese-American astrophysicist.

John Richard Gott III (born February 8, 1947) is a professor of astrophysical sciences at Princeton University. He is known for his work on time travel and the Doomsday argument.

Robert Paul Kraft (June 16, 1927 – May 26, 2015) was an American astronomer. He performed pioneering work on Cepheid variables, stellar rotation, novae, and the chemical evolution of the Milky Way. His name is also associated with the Kraft break: the abrupt change in the average rotation rate of main sequence stars around spectral type F8.

Harold Lester Johnson (April 17, 1921 – April 2, 1980) was an American astronomer.
Harold Johnson was born in Denver, Colorado, on April 17, 1921. He received his early education in Denver public schools and went to the University of Denver, graduating with a degree in mathematics in 1942. Johnson was recruited by the MIT Radiation Laboratory to work on World War II related radar research. After the war Johnson began graduate studies in astronomy at University of California, Berkeley where he completed his thesis under Harold Weaver in 1948.
In the following years working at Lowell Observatory, University of Wisconsin–Madison, Yerkes Observatory (where he met William Wilson Morgan), McDonald Observatory, University of Texas–Austin, the Lunar and Planetary Laboratory in Tucson, Arizona, and the National Autonomous University of Mexico he applied his instrumental and electronic talents to developing and calibrating astronomical photoelectric detectors.
He died of a heart attack in Mexico City in 1980. He and his wife, Mary Elizabeth Jones, had two children.
Johnson was awarded the Helen B. Warner Prize by the American Astronomical Society in 1956. He was elected to the National Academy of Sciences in 1969. He is remembered for introducing the UBV photometric system (also called the Johnson or Johnson-Morgan system), along with William Wilson Morgan in 1953.

Lawrence Hugh Aller (September 24, 1913 – March 16, 2003) was an American astronomer. He was born in Tacoma, Washington. He never finished high school and worked for a time as a gold miner. He received his bachelor's degree from the University of California, Berkeley in 1936 and went to graduate school at Harvard in 1937. There he obtained his master's degree in 1938 and his PhD in 1943. From 1943 to 1945 he worked on the Manhattan Project at the University of California Radiation Laboratory. He was an assistant professor at Indiana University from 1945 to 1948 and then an associate professor and professor at the University of Michigan until 1962. He moved to UCLA in 1962 and helped build its astronomy department. He was chair of the department from 1963 to 1968.His work concentrated on the chemical composition of stars and nebulae. He was one of the first astronomers to argue that some differences in stellar and nebular spectra were caused by differences in their chemical composition. Aller wrote a number of books, including Atoms, Stars, and Nebulae, the third edition of which was published in 1991 (ISBN 0-521-32512-9). He published 346 research papers between 1935 and 2004.
He was elected to the American Academy of Arts and Sciences in 1961 and to the United States National Academy of Sciences in 1962. He won the Henry Norris Russell Lectureship in 1992.
His doctoral students include James B. Kaler and William Liller.As of 2011, one of his three sons, Hugh Aller, was a professor and his daughter-in law, Margot Aller, a research scientist in the University of Michigan astronomy department. His granddaughter, Monique Aller, was previously a graduate student also in the University of Michigan astronomy department and teaches in the Physics and Astronomy Department at Georgia Southern University.

Donald Edward Machholz (October 7, 1952 – August 9, 2022) was an American amateur astronomer who was credited with the discovery of 12 comets that bear his name.

Kenneth Linn Franklin (March 25, 1923 – June 18, 2007) was an American astronomer and educator. Franklin was the chief scientist at the Hayden Planetarium from 1956 to 1984 and was co-credited with discovering radio waves originating on Jupiter, the first detection of signals from another planet. He was often a local and national media figure including during Apollo 11, the first human mission to the moon, when Franklin was an on-camera astronomy expert for NBC.