Bok, Bart J(an) (1906–1983)

Dutch-born US astrophysicist who discovered small, circular dark spots in nebulae (now Bok's globules). His work broadened our understanding of the formation of stars.

Bok, born in Hoorn, was educated at Leiden and Groningen in the Netherlands and in the USA at Harvard, where he remained and became professor 1947. In 1957 he went to Australia as head of the Department of Astronomy at the Australian National University as well as director of the Mount Stromlo Observatory near Canberra. He ended his career as professor at the University of Arizona 1966–74.

Photographs had shown that the Milky Way was dotted with dark patches or nebulae. Bok also discovered small, circular dark spots, which were best observed against a bright background. Measurements of their dimensions and opacity suggested that their masses were similar to that of the Sun. Bok suggested that the globules were clouds of gas in the process of condensation and that stars might be in the early stages of formation there.