Bartholomeus Jan "Bart" Bok (April 28, 1906 – August 5, 1983) was a Dutch-born American
astronomer, teacher, and lecturer. He is best known for his work on the structure and evolution of the
Milky Way galaxy, and for the discovery of
Bok globules, which are small, densely dark clouds of interstellar gas and dust that can be seen silhouetted against brighter backgrounds. Bok suggested that these globules may be in the process of contracting, before forming into stars.