Bart Jan Bok (Hoorn, 28 April 1906 – Tucson, 5 August 1983) was a Dutch-American astronomer.
He was born in the Netherlands, but spent a good deal of his childhood days growing up in what was then known as the Dutch East Indies. He was educated at the Leiden and Groningen Universities. In 1929 he married fellow astronomer Dr. Priscilla Fairfield Bok, and for the remainder of their lives the two collaborated closely on their astronomical work. They had two children, Joyce and John.
From 1929 until 1957 he worked at Harvard University. He then worked as director of Mount Stromlo Observatory in Australia for nine years, before returning to the United States as director of Steward Observatory. He became a US citizen in 1938.
In 1975 Bok coauthored the statement Objections to Astrology (The Humanist, 1975), which was endorsed by 186 professional astronomers, astrophysicists, and other scientists, including nineteen winners of the Nobel Prize. The statement was published in The Humanist. This led to the formation of the Committee for the Scientific Investigation of Claims of the Paranormal, of which he was a founding Fellow.
Bart Bok was an exceedingly popular personality in the field of astronomy, noted for his affability and humor. The Asteroid (1983) Bok was named for him while he was still living. In the ceremony announcing the award, he thanked the IAU for giving him "a little plot of land that [I] can retire to and live on." He participated in or led several groups to view solar eclipses, including a trip to the eclipse near Bratsk in Siberia in July 1981. On this trip to the USSR he led the group on a side trip to Byurakan Observatory, meeting with the director, Victor Ambartsumian.
His last eclipse trip was to return to what he called his "spiritual home" of Java to view a totality that passed near the town of Salatiga in June 1983. The night before the eclipse he spoke of his deep and abiding affection for the Indonesian people and said "If you wish to know Indonesia, eat Indonesian food and listen to gamelan music." He also spoke of how much he had enjoyed sharing his love of astronomy with others over the years.
Dr. Bok was nominated an honorary member of the Royal Astronomical Society of Canada on 1959-01-14. His biography, The Man Who Sold the Milky Way: A Biography of Bart Bok, was written by the Canadian astronomer David H. Levy. The asteroid (1983) Bok is dedicated to him.